Given its aliases as “Hawaiian Strombus” and “Strombus maculatus,” the Collumbellid euplica snail may not have its nomenclature, especially to the species level, all settled. But that doesn’t change how awesome of a snail it is. As shown below, they reproduce faster than rabbits (or for that matter, faster than my Stomatella hitchhiker snails!) They stay small, graze over rocks, and fit into the smallest nooks and crannies. As the algal population waxes and wanes, so, too, does their population for a harmonized tank. Back when Collumbellid snails were covering my tank, I decided to join the Marine Breeding Initiative. This was my journal entry documenting the breeding. Some of it may be a bit repetitive, but it was required for the breeding documentation.
Collumbellid Snail, also known as Hawaiian Strombus Snail
General Information:
GeneralSpecies:Columbellid euplica
Social Structure: Group
Size of Individuals: 1/2″ long
Age of Individuals: Unknown
Date added to Tank: May 2009
Collumbellid Snail, also known as Hawaiian Strombus Snail
Broodstock Tank Details:
Size of Tank: 40g Substrate Details: Bare bottom Filtration Details: Live Rock, Skimmer, Carbon/GFO Reactor Water Changes: 10% Weekly Water Temperature: 76 degrees Lighting: 6 x 39W T-5 Lighting Cycle: 8 hours on Other Tank Inhabitants: Blue legged crabs, nerites, corals
Broodstock Tank Feeding Details:
Food Types: Formula Two Pellets and DIY Frozen Blended Seafood Feeding Schedule: 2x/week
Spawning Details:
Date of First Spawn: Within days after introduction to the aquarium Spawn Time of Day: Unknown
Dates of Consecutive Spawns: Constantly?
Courtship Details: None apparent yet
Egg Size: <1mm
Egg Color: White
Egg Count: 6-7 in each packet
Collumbellid Snail Egg Masses laid on 1/27/2012
Collumbellid Snail Egg Masses laid on 1/27/2012 – closeup
Collumbellid Snail Egg Masses status on 2/2/2012 – closeup
Collumbellid Snail Egg Masses status on 2/6/2012 – closeup
Hatch Details:
Hatch Date: 2/6/2012
Hatch Time of Day: Unknown
# Days after Spawn: ~28 days
Larvae Description: Adult-like
Hatching Collumbellid snails (from a different spawn)
Larval Tank Details:
Temperature: 76 Size of Larval Tank: 40g Substrate Details: Bare Bottom Other Tank Decor: Live Rock Filtration Details: Live Rock, Skimmer, GFO/Carbon Media Reactor Lighting: 6 x 39W T-5 Lighting Cycle: 8 on Water Changes: 10% weekly
Larval Tank Feeding Details:
Food Types: Algae Feeding Schedule: Constant
Metamorphosis/Settlement:
Date of Settlement Start: N/A Days after Hatch: N/A Date of Settlement End: N/A Description of Fry: Appear as small adults
Juvenile Collumbellid Snail Size Reference with Hydroid
Week-old Juvenile Collumbellid Snail
Grow-Out Tank Details:
Temperature: 76 Size of Grow-Out Tank: 40g Substrate Details: Bare Bottom Other Tank Decor: Live Rock Filtration Details: Live Rock, Skimmer, GFO/Carbon Media Reactor Lighting: 6 x 39W T-5 Lighting Cycle: 8 hr on Water Changes: 10% weekly Size at Transfer: N/A Age at Transfer: N/A
Grow-Out Feeding Details:
Food Types: Algae Feeding Schedule: Constant
Additional Information:
Update 14 June 2012: I’ve found that these snails are able to make some sort of mucus thread that they are able to slide down in order to drop themselves lower in the tank. I also got to watch a snail glide across the top of the water surface, make a thread (only held by the surface tension), and then drop down to the bottom of the tank. It’s quite fascinating to watch!
Hearing the words, “green hair algae,” “Bryopsis,” “bubble algae,” and some species of Caulerpa are enough to send some aquarists begging for mercy. Thankfully, in the algae world, not all is bad. There are the good, the bad, and the plain ol’ ugly. These are some of the green marine algae I’ve come across throughout my reefkeeping days.
Algae falls under three phyla with the red species as Rhodophyta, the green as Chlorophyta, and the brown under Chrysophyta. Some good species (and readily available in the hobby) of green algae are Chaetomorpha, Halimeda, and Ulva; some nuisance species are green hair algae, Valonia, and Bryopsis.
Bornetella sphaerica: Not Reef Safe
Although this one small ball of Bornetella sphaerica green marine algae looks like a cluster of Valonia sp., it is just one singular mass. Thankfully, it is not very common in reef tanks.
When I started in the reefkeeping hobby, Bryopsis algae was one of the worst plagues, especially of all the green marine algae. Practically nothing eats it in large quantities, it takes over everything, and it can grow in just about any aquarium, regardless of nutrient and light levels. Thankfully, there are now some very effective treatments.
Bryopsis looks like long feathery strands of green algae, and short clumps of it can sometimes be confused with green hair algae.
For the most part, I really, *really*, don’t like Caulerpa in reef aquariums. While beautiful in species-specific tanks, it can wreak havoc on a beautiful, clean system. Many species of Caulerpa “go sexual” and can spread invasively throughout an aquarium. Manual removal is difficult due to strong hold-fasts (root-like structures that secure the algae from floating away) that can grow deep into rockwork, and manual removal usually ends in breakage (from which the algae can regrow). Often, very few reef tank inhabitants eat these algae, as many are quite noxious. While it’s a beautiful algae genus, I only recommend it for specialized aquariums only (such as macroalgae aquariums or “natural” reefs).
Caulerpa nummularia (“Mermaid’s Cup”): Reef Safe with Caution
Caulerpa nummularia is no exception. Although it has very unique “mushroom-shaped” cups, I recommend this only for macroalgae aquariums or “natural” reef aquariums.
Since this algae was quite unhealthy, the distinguishing serrated edge is difficult to see. Caulerpa brachypus looks quite similar to Caulerpa prolifera with the addition of small points along the leafy frond edges. Once again, this species of Caulerpa follows the typical behavioral characteristics of its parent genus and is probably best kept out of a typical reef aquarium.
Caulerpa serrulata has blade-shaped fronds and is also known for “going sexual” in an aquarium. Again, the holdfasts can grow deep into rockwork, and manual removal usually ends in breakage.
Caulerpa taxifolia is a fern-like species on the Federal Noxious Weeds list and is nicknamed the “killer alga” due to its invasive and toxic nature. Use caution, as “No person may move a Federal noxious weed into or through the United States, or interstate….” (See the Federal Noxious Weed Act for full regulations.) This “weed” has outcompeted native seagrasses in the Mediterranean and off the coast of California. It is very tolerant of poor conditions and has few predators. Best method of eradication is manual removal. Caulerpa mexicana is very similar to Caulerpa taxifolia but has more tightly-segmented fronds.
Caulerpa ashmeadii (“feather” Caulerpa): Not Reef Safe
Although very similar to Caulerpa toxifolia, this may be Caulerpa ashmeadii or Caulerpa sertulariodes (this was a very unhealthy sample, so a proper identification is difficult). Due to its similarity in appearance and behavior, it is probably not an ideal reef tank macroalgae.
Similar to Caulerpa brachypus, Caulerpa prolifera (in the front right of the photo) has tall, leafy green fronds extending from a wandering root structure. However, Caulerpa prolifera is missing the hallmark characteristic of the serrated edges of Caulerpa brachypus.
Caulerpa racemosa (“Grape Caulerpa”): Reef Safe with Caution
Despite growing Caulerpa racemosa for years, I do not have a photograph of it for some reason. Regardless, it is a vine-looking type of Caulerpa that resembles grape vines with small clusters hanging off the main stems. Although it shares characteristics with many other species of Caulerpa, it seems to “go sexual” less and has weaker hold-fasts than other species. To be honest, this species holds a small, special place in my heart, as I often traded bagful’s of it with my local fish store in exchange for my beginner-level corals.
Chaetomorphasp. Marine Algae: Reef Safe
Chaetomorpha is one of the most commonly encountered reef tank macroalgae. It grows in long spaghetti-like masses and readily utilizes nitrates and phosphates.
I do not have a great identification on the algae in the photograph, but a species of Cladophora (maybe C. pellucida?) is currently my best guess. This algae is more wiry and less fern-like than Bryopsis, which made it easy to remove from the rockwork.
Derbesia sp. (“Green Hair Algae (GHA)”): Reef Safe with Caution
Green Hair Algae (“GHA”) is just what it sounds like…green algae that looks like a hairball. Hermit crabs, snails, etc. may eat it, as long as it doesn’t get out of control. Cleanup crews usually will not touch massive mats of GHA. I recommend manually removing as much GHA as possible to allow the cleanup crew to effectively remove the remnants. Limiting nutrients through reduced feeding, skimming, running granular ferric oxide (GFO) and activated carbon (AC) may help slow GHA’s growth. Adding a refugium with “good” macroalgae, such as Chaetomorpha, can help outcompete the GHA.
This alga can be found in new, cycling aquariums, although I do occasionally find it growing in my tank whenever I know it’s time to replace my cleanup crew. Typically, it only grows to about two inches (about five centimeters) in length, although I have seen a few pieces grow to over 10 inches (about 25 centimeters). It is a cylindrical type of algae in the Ulva family (very palatable algae), and it is apparently quite delicious to my cleanup crew. Similar to the more leafy type of Ulva, it prefers cooler water (typically 77 degrees Fahrenheit or below) and higher nutrient water.
Although it’s not the most visually appealing algae, it’s a sign of good things to come in a new aquarium (and a sign of some issues in an established tank.) These microalgae films usually appear during the first couple of months of a new tank cycle, and they can cover the glass/ acrylic, rock, and sand. For a new aquarium, this is a critical part of the cycle: this algae feeds and helps establish a pod population! If it becomes a nuisance, it can be removed manually by scraping it or by utilizing a cleanup crew. It can also be reduced by limiting the nutrients in the aquarium.
As a calcareous type of marine algae, Halimeda grows slowly and does not become invasive. It requires a stable supply of calcium and seems to prefer lower nutrient levels. This algae can make a beautiful backdrop for macroalgae tanks, decorative refugiums, or even “natural-looking” reef tanks as it is not a target for most clean-up crews.
Not to be confused with Brown Clove Polyps, this green marine algae grows green flower-like fronds supported by a calcified stem. They do not appear to proliferate much in home aquaria; in fact, these only appeared for about a month on a shell, then vanished. They are typically found in shallow, warm water (above 78 degrees Fahrenheit). The most crazy part about this alga is that it is unicellular; the nucleus is found at the base of the stalk.
Ulva grows in large, floating sheets, and in the wild it tends to grow nearer to the shore. Its natural habitat suggests it prefers higher (but gentle) flow, high light, and high nutrients. This makes it a difficult algae to cultivate in a reef aquarium as most aquarists place macroalgae in low flow, low light areas with competitive algae (such as Caulerpa and Chaetomopha.) Additionally, this algae is a great food source for…well…just about everything. Herbivorous fish love it, as do snails, pods, and even bristleworms up to a point. The algae shown was in a 10g aquarium with about 65gph turnover rate and a 150W metal halide lamp over it.
Update [6/6/2023]: As one of the readers shared in the comments below, if/when Ulva “goes sexual,” it turns into a nuisance, with growths nearly everywhere. Interestingly, according to various posts, nothing seems to eat it (or eat it fast enough) at this point. While I haven’t dealt with this personally, I would assume Fluconazole would take care of it.
Valoniamacrophysa (“Green Bubble Algae”): Not Reef Safe
Although green bubble algae won’t choke out a reef quite like Caulerpa, Valoniamacrophysa is extremely invasive. Very few reef-safe inhabitants eat it, but some emerald crabs will (as always, just because some do, doesn’t mean all will.) The best prevention for this algae is a good quarantine system and manual removal outside the aquarium. There are some products available now that have varying degrees of success with eradicating it (although they come with their own risks of use).
Valonia aegagropila (“Green Bubble Algae”): Not Reef Safe
Here is another example of green bubble algae, possibly Valonia aegagropila (although it is missing the characteristic branching segments, but this colony may be to small for branching yet). Fortunately for my aquarium, there wasn’t enough present for a good identification.
This calcium-based algae is always a treat for me to see. It is not often found in home aquaria, and when it does appear, it seems to require a narrow set of parameters to thrive (I’ve only seen one case where these started to reach nuisance levels).
And then, there are the unidentified green marine algae, like this one shown in the foreground (note the Halimeda and Padina, along with some other species). With over 1500 known species of green marine algae, there’s no way this blog can cover them all. What neat species have you found? Post up in the comments!
From hairy to pointy and brown to neon orange, marine crabs vary spectacularly! However, they are omnivorous and opportunistic feeders, so monitoring should be utilized in all cases where the crabs are housed along with fish, snails, corals, or other undesirable food sources. If they are not fed adequately, they will resort to eating what they can find. These characteristics should highlight the importance of proper identification and selection of marine crabs. Additionally, crabs grow by molting, so it is not uncommon to see what appears to be a dead crab in the aquarium with the real crab hiding within corals or the rocks to protect its soft new shell. Scroll down to read more about the wide variety of crabs frequently encountered in the marine aquarium hobby. Note: There are several species included here that are not technically true “crabs” taxonomically, but they are grouped as such for hobbyist-level information.
Red legged crabs are great scavengers by feeding on algae, remaining fish food, and detritus. However, if the food supply gets too low (or they like a snail’s shell better than theirs), then they will kill snails. Because of this, keep enough food for the crabs (which is usually not a problem in most aquariums) and an available supply of various size/color shells.
Clibanarius vittatus (Green/Thin Striped Hermit Crab): Not Reef Safe
We named this little fellow, “Godzilla,” for his tremendous strength and bulldozing capabilities. These crabs are not reef safe (at least in my opinion, but others disagree) since they grow quite large and will eat just about anything (including ripping one of my corals to shreds to eat the food the coral caught). However, these are great scavengers for a non-reef tank without predators, as they are able to survive a wide variety of temperature and salinity ranges. Plus, they’re a lot of fun to just watch!
Out of all crabs available for a cleanup crew, these are the only ones I feel at all comfortable recommending. They are great scavengers, and their small size allows them to maneuver throughout the aquarium rather well. They eat many types of algae, detritus, and leftover fish food. Provide plenty of extra shells in various sizes and colors so the crabs will not kill snails for their shells.
Calcinus elegans (Electric Blue Hermit Crab): Reef Safe
Although similar in size and shape to the more common blue-legged crabs, the Electric Blue hermit crabs are much more brilliant. They are also somewhat more aggressive, in my experience. But, like the blue-leegged crabs, they are still great scavengers, and their small size allows them to maneuver throughout the aquarium rather well. They eat many types of algae, detritus, and leftover fish food. Provide plenty of extra shells in various sizes and colors so the crabs will not kill snails for their shells.
Dardanus megistos (White Spot Reef Hermit Crab): Not Reef Safe
This beautiful (and massive) hermit crab is far from reef safe as it can grow extremely large, be extremely predatorial, and also be very destructive. It is best kept in a fish-only (species limited to those that will co-exist, of course) or in a species-specific aquarium. They can also be housed in larger sumps with regular feedings.
Manucomplanus varians (Staghorn Crab): Not Reef Safe
This neat crab has a symbiotic relationship with its shell. The shell is composed of stinging creatures (similar to jellyfish), called hydroids and bryozoans. The shell of hydroids/ bryozoans protects the crab from predators. When the crab eats, pieces of food remnants are often caught by the hydroids/ bryozoans. As the shell grows, the crab trims the opening with its claws.
Although this is a very unique crab, it is not recommended for most reef aquariums as the shell itself requires special care. The organisms on the shell may die if the aquarium is not mature and stable enough. Additionally, these stinging creatures may harm corals, or corals may harm it. Lastly, due to the unique shape of the shell, the crab may not be able to right itself if it falls over.
Xanthid Crabs
Xanthidae Crab: Not Reef Safe
Since there are several hundred species in the family Xanthidae, identifying this particular crab to the species level is rather difficult. However, black-tipped claws are a good indicator that this crab is bad news (not all black-tipped crabs are bad though). Xanthid crabs typically enter the aquarium world by hitchhiking on live rock or corals. They use their strong claws to enlarge hiding spots in the rock, which ultimately weakens the rock. Even worse is if they decide to nest in a coral since they will carve out a hole and destroy the surrounding tissue. Xanthid crabs are known to eat almost anything and are very destructive in the process. Recommend removal from a reef aquarium as soon as possible. Occasionally soda bottle traps work, but typically homemade spears work best. If removed safely from the reef aquarium, I recommend keeping these crabs in a species-specific tank or suitable sump as they are very interesting to watch.
Possibly Pilumnus vespertillo (Gorilla Crab): Not Reef Safe
This is another example of a Xanthid crab (the black-tipped claws are hidden under its body.) This is one of the many crabs that falls under the generic name, “gorilla crab”. Recommend relocation from a reef aquarium to a suitable sump or species-specific tank. See above for more information.
Possibly Polydectus cupulifer (Teddy Bear Crab): Not Reef Safe
This is another example of a Xanthid crab, and this is one crab that frequently falls under the common name, “Teddy Bear Crab.” It is also frequently called a “Gorilla Crab”. See above for more details/warnings on Xanthid crabs.
Mithraculus sculptus (Emerald/Ruby Crab): Reef Safe with Caution
Like many crabs for the home aquarium, the emerald Mithrax crab may become overly aggressive as it grows. While small, the emerald crab is another great scavenger, and is one of the few crabs known for removing bubble algae (Valonia) (some eat it more readily than others). The emerald crab may also damage SPS corals as it becomes larger by literally taking out chunks to eat. If you have a mature reef, you may not notice the damage, but if your tank is full of small coral fragments, the damage may be tremendous. Although the emerald crab is mostly available in green (hence the name), a red Mithrax variety is also sometimes available.
Stenorhynchus seticornis (Arrow Crab): Reef Safe with Caution
The arrow crab is quite unique and is ok for a reef aquarium without small fish (arrow crabs are known to catch small fish). Additionally, arrow crabs are known to eat the occasional bristle worm and may help control the population.
In the wild, I typically see them with corkscrew anemones (Bartholomea annulata) or branching anemonees (Lebrunia sp.), and sometimes even with Pederson shrimp.
Arrow Crab with a Corkscrew AnemoneArrow Crab and Pederson Shrimp in Branching Anemone
Pom Pom Crabs are… well… just awesome. They are beautifully colored, carry anemones for protection, and act like boxers about to take a swing. They carry tiny anemones on the tips of their claws for protection. If they feel threatened, they will sway their arms out and occasionally strike an opponent with the stinging anemone. In exchange for the anemone’s protection for the crab, the crab helps feed the anemones. The crab’s anemones may sting and damage typical reef inhabitants (e.g., corals, crabs, fish), so caution is urged. However, this crab can be rather secretive, so potential damage is limited.
Percnon gibbesi (Sally Lightfoot Crab): Reef Safe with Caution
The Sally Lightfoot Crab is a scavenger and looks for detritus and dying matter to eat. Its body shape allows it to fit into very tight places in the rocks and to run quickly to safety. While the crab is great when smaller, as it grows it becomes more aggressive and may prey on small fish. Keep in mind how hard this crab will be to catch as it grows if it becomes a problem.
Zebrida sp. (Zebra Urchin/ Thorn Crab): Expert Only with Special Setup
The Zebra Urchin Crab, also known as the Zebra Thorn Crab, is an obligate symbiont of sea urchins. This means that both depend on each other for long-term survival.
Here is a female gall crab (notice the yellow eggs). Typically the females burrow into a coral and live out their lives in a small tunnel or hole (see image below with the red circle), while the males roam free. I often find these associated with struggling corals (as in the example shown), but I am not convinced that they cause the coral’s decline. The female does burrow and create a small amount of damage, which may lead to a bit of stress in the coral. However, a healthy coral should be able to tolerate this. I guess the jury is still out, but until then, I’ll appreciate the diversity they bring to a reef.
Majoidea superfamily (Decorator Crab): Reef Safe with Caution
Do you see it? Good, neither do I. The Decorator Crab uses whatever is available (e.g., sponges, corals, anemones, rocks, shells, food) to adorn the small hairs covering its body as camouflage and protection. This crab can be reef-safe, depending on how it decorates. But, do not be surprised if small frags go missing, as this crab may take zoanthid polyps, pieces of leather coral, or other small snippets for personal use.
Not only are “Berghia Nudibranchs” (Aeolidiella stephanieae) elegant, with their glowing blue-white cerata, but they are also amazing natural Aiptasia anemone predators. Originating from the Florida Keys, once introduced to an Aiptasia-infested aquarium, the nudibranchs band together at night to hunt and take down the anemones, one-by-one. At first, this is a slow process, but the nudibranchs reproduce quickly enough to out-compete the anemones. Understanding a few key concepts on the nudibranch’s lifecycle, natural predators to avoid, and basic care may help eradicate Aiptasia from an aquarium.
Berghia Nudibranchs Eating an Aiptasia Anemone
Lifecycle of Berghia Nudibranchs:
Egg Development:
Mature nudibranchs (about five to seven weeks old) lay egg masses in beautiful spirals with less than 100 eggs initially to more than 250, approximately every four days. As the nudibranchs mature, they lay more eggs per mass, more frequently. I currently have one pair that returns to the same place in the aquarium every two nights to lay eggs together (they appear uninterested in the other nudibranchs, which may be due to their extra-large size).
Egg development occurs over the course of about 12 days, as shown in the photos below.
Berghia Nudibranch Egg Spiral Day 0Berghia Nudibranch Egg Spiral Day 2Berghia Nudibranch Egg Spiral Day 3Berghia Nudibranch Egg Spiral Day 5Berghia Nudibranch Egg Spiral Day 7Berghia Nudibranch Egg Spiral Day 12
Metamorphosis:
This short stage (approximately one-to-three days) of Berghia nudibranch development is my favorite. The nudibranchs hatch into these rice-shaped fluorescent blue larvae, which look very similar to their adult cerata. I was collecting some adults one day, when I saw these floating on the underside of the surface of the water. They tend to float upward and stay until metamorphosis is complete, which may make them a target for fish to eat.
This photo shows a larval Berghia Nudibranch, along with a juvenile (a week or two old post-hatching). After metamorphosis, the juveniles settle back into the rocks to begin hunting Aiptasia. As they are extremely small, they tend to attack only the smallest anemones, likely to avoid being eaten.
Adult Berghia Nudibranchs
Similar to the juvenile nudibranchs, the adults band together to hunt anemones, but as they grow, they are able to prey on larger anemones. A well-fed nudibranch will take on the brown coloration, as shown, from ingesting and retaining the anemones’ zooxanthallae.
Hunting in groups, along with their hermaphroditic nature, typically provides plenty of mating opportunities. With egg masses over 100 laid every few days, the population can quickly outpace the food source (the nudibranchs can starve in around five days without food). Provided with enough food and protection, the nudibranchs will live approximately 10-12 months. However, Berghia Nudibranchs do face several threats in the home aquarium.
Aquarium Husbandry:
General Information:
Unfortunately, Berghia Nudibranchs are not as tolerant of poor water conditions as Aiptasia; they require stable parameters within natural saltwater conditions. Additionally, they are prey for a variety of wrasses (but thankfully the nudibranchs’ nocturnal nature helps protect them), and the egg masses and juveniles are prey for amphipods. Even Aiptasia will eat the nudibranchs if they are lucky enough to catch one.
Selection:
Typically, for a moderate Aiptasia infestation, one Berghia per 10-gallons is recommended (see the table below). However, since Berghia nudibranchs hunt in groups and need to reproduce, never introduce less than three, regardless of tank size. For example, three nudibranchs would be an appropriate number for a 30-gallon aquarium, a 10-gallon aquarium, and also a 1-gallon aquarium. Even then, it is best to overestimate to ensure the nudibranchs can find each other to breed. In other words, if the tank size falls between the recommended quantities below, round up.
Size also matters. While smaller nudibranchs cost less, they also may not reproduce for a few more weeks. They are also less able to attack larger Aiptasia or withstand high-flow aquariums (e.g., SPS-dominant). In tanks with high flow, larger predators, heavy infestations, and/or large Aiptasia, mature adults are best. For low-flow tanks with light Aiptasia infestations, a mixture of medium and small nudibranchs may work best.
Tank Size
Initial Berghia Nudibranchs*
1-gallon
3 Medium Nudibranchs
10-gallons
3 Medium Nudibranchs
30-gallons
3 Medium Nudibranchs
40-gallons
4 Medium Nudibranchs
75-gallons
8 Medium Nudibranchs
90-gallons
9 Medium Nudibranchs
120-gallons
12 Medium Nudibranchs
150-gallons
15 Medium Nudibranchs
300-gallons
30 Medium Nudibranchs
Recommended Berghia Nudibranch Starting Populations (*for medium flow, moderate-infestation tanks)
[NOTE: If you are looking for a source of Berghia Nudibranchs, please see Reference #4 at the end of this article for a potential source. This page is not currently affiliated with any nudibranch vendors.]
Introduction into the Aquarium:
If the nudibranchs were shipped, they are likely more white colored due to a lack of food. And, depending on the temperature conditions during shipping, they may appear quite sluggish. They likely came in a jar, similar to the one shown here. Never place this jar to float in the tank for acclimation, as the jar’s motion may tumble the nudibranchs. Instead, slowly remove the jar’s water, while adding the same amount of tank water back into the jar, over the course of about 30 minutes to an hour. This will enable the nudibranchs to adjust to the tank while minimizing injury. Next, turn off all flow in the tank, and if there are predator fish, wait until the lights go off.
Place the jar in the rocks (not on the sand) near (but not on) some Aiptasia anemones. Allow the nudibranchs to crawl out naturally on their own. If they are sluggish or the flow needs to be restored to the tank, use a pipette with the end cut off to gently baste them out of the jar.
Final Thoughts and Conclusion:
It’s important to remember that nudibranchs are only a natural control, not a cure; they cannot reach every place Aiptasia may infest. After tank introduction, it is common to not see the Berghia nudibranchs (or evidence of their existence) for months later (until seemingly overnight, the Aiptasia start vanishing!) It is only once the nudibranchs’ population reaches a “critical mass” point that they really make a difference.
Monteiro, Estela A., et al., “Implications of feeding frequency, prey size and condition, and intraspecific competition for the commercial aquaculture of the nudibranch Berghia stephanieae,” Journal of the World Aquaculture Society, February 2020. https://onlinelibrary.wiley.com/doi/full/10.1111/jwas.12645
In my years of reefkeeping, I’ve seen some odd stuff. But, back in 2013, I was stumped. My corals were receding like something was eating them, but no matter how long I watched the corals at 3 a.m., I couldn’t find the culprit. I had heard of Acropora “black bug” parasites, but I couldn’t find any pictures of them. I really wasn’t convinced they actually existed in the hobby, or if they did, that I had them.
Speck on Acropora Coral
One day, I noticed the tiniest gray speck of movement on an Acropora coral. I watched it for a while, but I wasn’t sure what I was seeing. It definitely wasn’t a red bug (Tegastes acroporanus), but it also did not seem like random detritus movement. I decided to err on the side of caution and dip the coral. (You see it, right??)
Alteuthellopsis corallina parasite on Acropora Coral
First, I started with Coral Rx, but the speck didn’t fall off. In fact, I couldn’t move the speck with a pick. When I grabbed a magnifying glass, I realized the tiny “pod” had lodged itself in the coral’s tissue and was still very much alive.
I then dipped the coral in a different dip, and the speck fell off. This is what I found under the microscope. Sorry for the poor quality – this was back in my sub-par microscope days.
Alteuthellopsis corallina or “Black Bug” Acropora Parasites:
Although I am not certain, I believe the parasites were Alteuthellopsis corallina (so we’re going to go with that assumption for the remainder of this post). These parasites are coral predators, and according to this article, they are known to infect Acropora, Merulina, Pocillopora, and other stony corals.
How to Identify:
While corals affected with red bugs tend to “brown out,” the corals infected with A. corallina appeared bleached and as though something was eating them. A. corallina are only a little larger than 0.5 mm, so they’re extremely difficult to see due to size and color. As mentioned above, this species seems to have an ability to lodge themselves into coral tissue. These parasites are more gray than black, but most reefkeeping websites reference odd pods as being black. In the hopes of providing the most information possible on Acropora parasites, A. corallina is associated with both gray and black bugs here.
In order to determine the presence of any sort of unusual pods, I typically use a magnifying glass to inspect the corals prior to placement in a quarantine system. After that, I observe the coral daily for a week. I also take a photo of the coral and zoom in to look for anything I missed.
If you suspect you have a pod problem, I recommend ruling out all other options (e.g., water quality, large pests, flow problems) Next, inspect the coral for movement since the human eye can spot movement somewhat better than a 0.5 mm stationary speck. Even if you can’t spot anything, a quick dip may indicate pest presence.
Treatment Options:
It appears likely that typical red bug treatments will work on the black/gray bugs, but I have been unsuccessful photographing or studying them further. Thankfully, in 14+ years of reefkeeping, I have only encountered these once.
Method 1: Control
Based on my experience with A. corallina, I can’t recommend natural controls. These pods can really lodge themselves into the coral tissue, and any pod predator would probably cause significant damage to the coral. Regardless, I advise against natural control methods for aquarists who plan to sell/trade their corals.
Method 2: Coral Dips
Coral dips often help stun the pests so they can be blown off gently with a pipette or powerhead. For live bearer parasites, this may be a one-shot treatment. Unfortunately, I don’t know how these parasites reproduce, so if you dip, I still recommend quarantine. Red bugs are live bearers, but I wouldn’t take any chances regarding applicability to A. corallina.
As mentioned above, CoralRx did not cause any noticeable harm to A. corallina at the manufacturer’s recommended dosage. It may work on other similar parasites, at higher dosages, or longer time, but I did not have enough pods to test this on. Other dips will likely work, as a different dip was successful for me.
Since a succession of coral dips work for Acropora-eating flatworms and red bugs, I dip all Acropora corals daily the first week. After that, I dip all Acropora corals every other day the second week, every third day the third week, and then once a week for weeks four through six. I have not lost a single coral with this method, and it saves me the hassle of treating with different medications for different parasites at different times.
Note: I have never found a pest after week two, but I still go the full six weeks, since the lifecycle of AEFW is quite long (and I always treat Acropora corals for both AEFW and red bugs). Also, some dips can be extremely damaging to smooth-skinned corals, so please use caution if you plan to utilize a coral dip.
WARNING: Some aquarists use Bayer Advanced Insecticide as a coral dip. Per Bayer Advanced Insecticide’s labeling, “It is a violation of Federal law to use this product in a manner inconsistent with its labeling.” Due to this warning, this website does not cover Bayer use as a coral dip.
Coral Dip Treatment Protocol for A. corallina Parasites:
Follow dip manufacturer instructions.
Method 3: Prescription Flea Medications
Hobbyists considered Interceptor (milbemycin oxime), a prescription canine flea medication, as the golden standard for red bug parasite treatment. At least, they did before the manufacturer discontinued it. Even then it was not the easiest solution. Aquarists had to remove all shrimp, crabs, and other crustaceans before dosing. This die-off would spike ammonia levels, so reefkeepers also had to prepare for a water change and to run carbon. Additionally, many people had difficulty obtaining Interceptor from their veterinarians, since this is an off-label use. Eventually, the Veterinary Information Network published information on red bug parasites for reference.
Once Interceptor was no longer available, reefkeepers began searching for a replacement. Currently, Milbemax is the most often recommended replacement. It is a prescription combination of milbemycin and praziquantel. The latter medication is commonly used for fluke treatment in reef tanks (e.g., PraziPro); however, it is a much lower dose than would be effective for common marine flukes.
Providing proof of infection to a veterinarian and asking him/her to look up red bugs on the VIN may be enough to justify the medication for gray/black bugs. Some veterinarians have recommended different medications with different treatment protocol (e.g., MilbeMite Otic), so those individual cases are not discussed here.
Unfortunately, many aquarists are finding some red bugs have a resistance to Milbemycin, so gray/black bugs may as well. If you try it with no success, work with your veterinarian to find an alternate medication, or consider one of the alternate methods described here. See the red bug page for more information on reference dosing protocols for both Interceptor and Milbemax.
Method 4: Temperature Adjustment
Many aquarists (including myself) have noticed red bugs die at lower temperatures, and this may be an acceptable treatment for gray/black bugs as well. A temperature of 72°F may be adequate to control/reduce the population. Use caution with this method as it can cause coral stress if the temperature drops too suddenly or if the oxygen level drops.
Due to a six-hour power outage in Utah, my quarantine tank dropped to 65 degrees. Afterward, there was no sign of red bugs on a known infested Acropora. Note: this is experimental, and there is not enough data to determine if this treatment works 100% or with gray/black bugs. Use with caution!
Conclusion:
It is truly terrifying and amazing what a 0.5mm speck of a pod can do to a coral. It is likewise amazing and rewarding how the Acropora coral can recover. With this sort of risk, a good quarantine is absolutely essential, but there are a few viable treatment options available.
Growing…growing…gone. Unfortunately, this is an all-too-common story in the reefkeeping hobby due to a pest aptly named for its favorite meal, the Montipora-Eating Nudibranch (Phestilla subodiosus). Although treatment of Montipora-Eating Nudibranchs is historically challenging, this article covers several available options.
Montipora-Eating Nudibranchs (M.E.N. – just kidding, I won’t use that acronym) are from the phylum Mollusc, class Gastropod, sub-class Opisthobranchia, order Nudibranchia. From there, they are of the suborder Aeolidina, superfamily Fionoidea, family Trinchesiidae, genus Phestilla, species subodiosus. Identification down to the species level was only accomplished as recently as 2021, although the hobby has been actively fighting them since at least the early 2000’s (Wang, et al., 2020).
How to Identify:
These nudibranchs are white in color and range in size from 1-3mm in length. The body is covered in cerata, which may store the nematocysts (stinging cells) of the coral to help protect them from predators. Shown in the picture is a single Montipora-Eating Nudibranch (circled in red) at the edge of a Montipora digitata coral.
The key to detection is to understand the life cycle of these nudibranchs. If there is only one nudibranch, it is capable of reproducing asexually. The adults lay tiny clusters of 3-20 eggs (Borneman, 2007) in crevices along the base of the coral (see image). As the eggs hatch, the juveniles immediately join the adults in eating the coral in a distinct jagged line along the base and edges. Reportedly, these nudibranchs can survive extended periods with no food source.
Back in grad school, I modeled the lifecycle of these nudibranchs and how various treatments worked on them. Unfortunately, the results were never promising once the nudibranchs established themselves in a mature tank. (Note: Sadly, I built this model with an educational license, and my files are “legacy file types” for the software. I have been unable to regain access to my work for either historical purposes or additional research.)
Montipora-Eating Nudibranch Treatment Options:
Treatment for the Montipora-Eating Nudibranchs comes in the forms of prevention, natural predators, chemical destruction, and manual removal.
Treatment Method 1: Prevention of Montipora-Eating Nudibranchs:
Prevention lies in purchasing from a reputable dealer or hobbyist first and foremost. Chances are, if the person has had them before, that person will have them again. Next, the responsibility falls to the new owner of the coral in proper quarantine procedures (at least two months is recommended). Examination with a magnifying glass is recommended to help identify and remove eggs. However, the nudibranchs might have laid eggs in a hidden crevice. Since the eggs are laid at the base of the coral or on dead coral skeleton, some hobbyists chose to remove the coral from the base rock. Both remaining coral on the rock and base rock then dies. This is to help ensure that the eggs are not transferred.
Treatment Method 2: Controls for Montipora-Eating Nudibranchs
Some hobbyists have found certain natural predators will help control the nudibranchs. Unfortunately there are no known complete eradication measures available naturally. The wrasses generally known to eat most invertebrates will most likely also feed on the nudibranchs. It is important to keep in mind that as far as natural predators go, what works for one hobbyist may not work for another hobbyist, especially with wild creatures.
Treatment Method 3: Coral Dips for Montipora Eating Nudibranchs
The last method of eradication is by chemical means. Coral dips often help stun the pests so they can be blown off gently with a pipette or powerhead. These adult Montipora-Eating Nudibranchs (as pictured) were in a dip much longer than the coral colony could survive. Unfortunately, that is typically the case; however, there are a few less lethal options.
Montipora-Eating Nudibranch Treatment: Iodine
Many hobbyists have found that an hour-long dip in iodine will kill most adult nudibranchs. However, this may cause undue stress to the host coral, especially if flow, pH, and temperature are not ideal in the dip.
Montipora-Eating Nudibranch Treatment: Levamisole
Levamisole (a pig dewormer available at farm supply stores), has been used in a similar manner to the iodine dip, but with a higher fatality rate to the host coral. Levamisole paralyzes the nudibranchs so they can be removed more easily from the coral.
Another chemical method is potassium permanganate. The dip (50mg/l for 30-90 minutes – Borneman, 2007) has been shown to effectively destroy both the adults and the egg masses with moderate impact to the coral. After eradication on the corals, the main tank should be kept free of Montipora for approximately two months.
Like all chemicals, caution should be exercised when handling potassium permanganate. Using an MSDS (Material Safety Data Sheet) to learn about the hazards of use and what protective gear is highly recommended. An MSDS for potassium permanganate suggests the use of eye protection, gloves, and respiratory protection as potassium permanganate can cause serious burns to the skin, nose, and throat.
Montipora-Eating Nudibranch Treatment: Series of Dips + Manual Removal
Rather than trying to kill both adult nudibranchs and eggs, I attempt to just break the lifecycle by removing the adults so that they cannot reproduce. When I get any frags of Montipora, I perform my usual coral intake process. I perform an inspection, remove the plug/base/dead skeleton, perform dips with manual pest removal, and attach a new base. Then I place the coral into my quarantine tank, but it stays for an extended period (60 days rather than the typical 30 days).
Since a succession of coral dips work for AEFW and red bugs, I also dip all Montiporas daily the first week to aid in manual removal. After that, I dip every other day the second week, every third day the third week, and then once a week for weeks four through six. I have not lost a single coral with this method, and it saves me the hassle of treating with different medications for different parasites at different times.
Various dips may work to stun the nudibranchs, and examples include CoralRx, Revive, and Tropic Marin Pro Coral Cure. Again, here the goal is to simply aid manual removal by stunning the adults. If the adults are removed, the eggs will continue to hatch in the presence of food. Adults are then easily removed before they can reach maturation. In the lifecycle model mentioned above, this was the most successful approach when implemented correctly.
Montipora-Eating Nudibranch Treatment: Display Tank + Dips
The worst challenge is a display tank with mature colonies infested with nudibranchs. My best advice is to consider the coral dip series described above (although large colonies may require buckets for treatments). Additionally, the hobbyist would have to kill any bases left attached to the rock along with unremovable encrusted Montipora colonies. Another option, if the colonies are smaller, may be for the hobbyist to remove all Montipora from the display tank. The hobbyist would then place all removed Montipora into a quarantine tank for treatment, minus a sacrificial frag that stays in the display. The hobbyist must then frequently replace that sacrificial frag so as to draw out the nudibranchs from the rockwork.
Montipora-Eating Nudibranch Treatment: Other Dip Options
Hobbyists have used garlic and freshwater dips with nudibranch mortality but they also often report high coral mortality.
Conclusion:
Although there are still no full-tank chemical treatments, eradicating Montipora Eating Nudibranch is possible with patience and proper husbandry. Using a combination of dips and manual removal seems to be the most effective option available at this time.
Somehow back in the day, after over five years of having SPS-dominant aquariums, I got my first case of red bug parasites. A local aquarist was tearing down his system and gave me a few corals that weren’t doing well. Turns out, red bugs AND Acropora-eating flatworms (AEFW) infested the corals. Fortunately, I caught the red bugs while the Acropora was still in my quarantine tank.
Red bug parasites (Tegastes acroporanus) are extremely tiny copepods (as seen in the red circle in the photo) that solely infest Acropora corals (not Montipora, Pocillopora, etc.) They come into the hobby on wild or maricultured colonies (corals purposefully grown and harvested in controlled ocean environments), and hobbyist selling/trading of aquacultured corals further spreads them.
A good indicator of a red bug infection is a loss of Acropora tip coloration and browning that cannot be attributed to other factors. Red bugs caused the coral shown to lose nearly all coloration, while AEFW caused the white patches.
In the early 2000’s (now I’m dating myself), there was a general consensus in the reefkeeping hobby that red bugs only affected smooth-skinned Acroporas. Hobbyists assumed they did not bother corals like Milleporas or “the green slimer” due to the extra mucus they produce. Although red bugs do tend to prefer certain Acropora (especially Acropora valida, the “tricolor”), most every Acropora species is susceptible. Hobbyists also commonly believed that red bugs laid eggs and had a larval stage. This led to a consensus that three treatments were needed in order to eliminate the red bugs entirely. Although research eventually determined that red bugs are live bearers, I still recommend three treatments just as a safety precaution.
How to Identify:
On Acropora corals that have “browned out” due to red bug presence, the red bugs are rather distinguishable. They are mostly yellow (almost a gold color) with a bright red dot. They are also extremely tiny at around 0.5mm (think a little bigger than the size of the period at the end of this sentence). Unfortunately, they are not easy to see on healthy corals, and they have an ability to hide within the coral polyp itself without being consumed. In order to determine the presence of red bugs, I use a magnifying glass to look for them before placement into my quarantine system. After that, I observe the coral daily for a week. I also take a photo of each coral and zoom in to look for anything I’ve missed.
How to Treat Red Bug Parasites:
Unlike other serious pests (e.g., Montipora-eating Nudibranchs), there is a suitable in-tank treatment for red bug parasites.
Method 1: Control
Some hobbyists believe that blowing the corals off with a powerhead a few times for a couple weeks will rid the Acropora of red bugs since they may starve before finding their way back to the coral. Other hobbyists rely on natural predation (e.g., pipe fish, file fish, gobies, wrasses), but to my knowledge, no predators have a 100% success rate. I advise against natural control methods for aquarists who plan to sell/trade their corals.
Method 2: Coral Dips
Coral dips often help stun the pests so they can be blown off gently with a pipette or powerhead. Since red bug parasites are live bearers, this method can work as long as all the red bugs are removed. Since a succession of coral dips work for AEFW and red bugs, I dip all Acroporas daily the first week. After that, I dip every other day the second week, every third day the third week, and then once a week for weeks four through six. I have not lost a single coral with this method, and it saves me the hassle of treating with different medications for different parasites at different times.
I should note that I’ve never found a pest after week two, but I still go the full six weeks since the lifecycle of AEFW is quite long (and I always treat for both AEFW and redbugs). Also, some dips can be extremely damaging to smooth-skinned corals, so please use caution if you plan to treat one of these.
Coral Dip Treatment Protocol for Red Bug Parasites:
Follow dip manufacturer instructions.
Method 3: Prescription Flea Medications
Before the manufacturer discontinued it, hobbyists considered Interceptor (milbemycin oxime), a prescription canine flea medication, as the golden standard for red bug parasite treatment. However, as it killed all shrimp, crabs, and other crustaceans, aquarists had to remove them before dosing (the pod population recovered with time). This die-off would also spike ammonia levels, so reefkeepers had to be prepared for a water change and to run carbon. Many people had difficulty obtaining Interceptor from their veterinarians since treating for red bugs is an off-label use. However, the Veterinary Information Network (VIN) published information on red bug parasites for reference.
Once Interceptor was no longer available, reefkeepers began searching for a replacement. Currently, Milbemax is the most often recommended replacement. It is a prescription combination of milbemycin and praziquantel. (The latter medication is commonly used for fluke treatment in reef tanks (e.g., PraziPro); however, it is a much lower dose than would be effective for common marine flukes).
Providing proof of infection to a veterinarian and asking him/her to look up red bugs on the VIN should be enough to receive the medication (or at least it was for us.) Some veterinarians have recommended different medications with different treatment protocol (e.g., MilbeMite Otic), so those individual cases are not discussed here. Unfortunately, many aquarists are finding some red bugs have a resistance to milbemycin. If you try it with no success, work with your veterinarian to find an alternate medication or try one of the other methods listed here.
Interceptor Treatment General Protocol for Red Bug Parasites:
(This is provided for historical purposes only since Interceptor is no longer available, as it may be relevant to other treatments.) Dustin Dorton of ORA determined 0.025 grams of Interceptor are needed per 10 gallons of water. After that, the protocol is the same as Milbemax, described below.
Milbemax Treatment General Protocol for Red Bug Parasites:
(Obtain actual procedures from a veterinarian, as this is for general reference only.) The recommended dosage is 23mg per 400g tank water, which works out to 0.0575mg per gallon tank water (or 5.75mg per 100 gallons if that is an easier reference point). Similar to Interceptor medication, pulverize and weigh the medication out as accurately as possible. Estimate the true volume of water as close as possible (subtracting live rock, sand, etc.)
Remove all crabs, shrimp, and other crustaceans from the aquarium before dosing. Turn down the skimmer so that water runs through it, but the skimmer doesn’t actually skim. Remove GFO and activated carbon. Add an airstone (or multiple, depending on the size of the tank) bubbling gently to help maintain the pH. Otherwise, allow everything else to run so that the chemical can spread throughout the aquarium. Dose the correct amount and let the system run for six hours.
After six hours, the red bugs should be gone, but if they are not, slightly adjust the dosage and try again in a few days. Perform a water change (~15-25%), turn the skimmer back up, and bring the GFO and carbon back online. As mentioned above, although red bugs are live bearers, three treatments a few days apart is still ideal. Once the red bugs are completely eradicated and the medication is removed, reintroduce the crabs, shrimp, and other crustaceans to the aquarium.
Method 4: Bayer Advanced Insecticide
WARNING: Per Bayer Advanced Insecticide’s labeling, “It is a violation of Federal law to use this product in a manner inconsistent with its labeling.”
Yes, this is the stuff you may have in your garage or at your local hardware store. Some aquarists use it as a dip only, not as an in-tank treatment. This website does not cover Bayer use as a coral dip, due to the warning above.
Bayer Advanced Insecticide
Method 5: Temperature Adjustment
With crazy heat in the summers, lowering the tank temperature may not be feasible. But for tanks located in basements during the winter, this may be the least expensive option. In fact, this method worked for me…accidentally! Right after I received the infested Acropora mentioned above, we lost power for about six hours. My quarantine tank got down to about 65 degrees (thanks to being in Utah in the middle of winter). After the power came back on, there were no signs of red bugs. I’m not the first to document this. I still continued treating for them just in case, but I never saw another one. This seems to work, but we still need scientific studies to back it up.
Experimental Temperature Treatment Protocol for Red Bug Parasites:
Slowly lower temperature to 65-66 degrees. If tank inhabitants start to show signs of stress, start bringing the temperature back up. Leave the temperature at 65-66 degrees for 4-6 hours. Note: this is experimental, and there is not enough data to determine if this treatment works 100% or is safe. Use with caution!
Conclusion:
Thanks to all the courageous mad scientist reefkeepers out there, there are several proven treatments for red bugs, including an in-tank treatment. The Acropora shown was saved from both red bugs and AEFW! Hopefully, with the increasing ease of treatment protocols, red bugs will be a thing of the past. Best of luck in your treatment!
A single dot, a squiggle of white, a floating orange ball – marine eggs come in all shapes, sizes, and colors! Of course, the easiest way to tell what it could grow up to be is to find mom nearby, but that’s not always possible. These are just a few of the most common eggs found in an aquarium to help you with the identification of marine eggs.
Anyone plagued by Aiptasia sp. anemones needs to know about Berghia nudibranchs. These nudibranchs only eat Aiptasia anemones, and they produce an egg sac like the one pictured every few days. Below, a microscope image shows the developing nudibranchs, along with grown adults.
Nerite snails are a great snail, but I only know of one person who had nerite eggs hatch and grow successfully to adults (in other words, most eggs do not become adults…or even make it to juveniles.) The eggs look like white sesame seeds and are sometimes found singularly or in small groups (like the four in the photo below). Read more about snails here!
Ok, so maybe the taxonomy isn’t entirely straightened out on this snail yet, but regardless of name, they’re great snails. As you can see by the multiple egg sacs, they reproduce faster than rabbits. If you’re sick of buying snails, then these are your best choice in my opinion. They graze over rocks and on glass, stay small, and their population waxes and wanes with food supply. Read more about snails here!
Nassarius snails produce various egg patterns, depending on species. Some of them produce some of the most beautiful “fan” patterns of marine eggs, but others leave these small individual sacs. Read more about snails here!
Cerith snails are a beneficial part of a reef tank clean-up crew. They reproduce in captivity to some extent (some aquarists have more success than others, and the juveniles make it to adulthood in small numbers). The egg pattern is very distinctive, as shown with the mother (and possibly father). The egg pattern will vary by species, but most have something similar to this white swerving pattern or the fuzzy white string below. Read more about snails here!
Stomatella snails are hands-down my favorite snail. They come in nearly all colors (like the black one and speckled one below, but also in red, silver, green, etc.) They frequently enter an aquarium as a hitchhiker, scour the tank for algae, and then reproduce prolifically. They’re broadcast spawners, so they reproduce by climbing high in the aquarium and releasing small puffs of sperm and eggs which look like smoke.
Although the stomatella snail can’t be seen in the photo with the Scolymia coral, there is one hiding under the coral releasing either sperm or eggs (white smoke-looking mass to the left of the Scolymia). This event lasted about 3 minutes. Unfortunately, I’ve had a hard time determining their life cycle times since they constantly have new batches of babies. Read more about snails here!
I had (what I assume to be) a mated pair of fighting conchs that regularly laid eggs. Unfortunately, I never had success raising these in captivity. Read more about conchs here!
Acropora-eating Flatworms (Amakusaplana acroporae) – Not Reef Safe:
As the common name implies, these flatworms only eat Acropora corals. Although they usually lay their eggs directly on the Acropora corals, the eggs can sometimes be found near Acropora corals, like on a frag plug in the photo.
These massive flatworms are not reef safe due to their predatory behavior. I found one of these flatworms inside a hole in the live rock attached to a coral along with the marine eggs shown. Although I am not 100% certain the eggs are from the flatworm, there were no other large invertebrates within the live rock. Additionally, the eggs resembled very large Acropora-eating Flatworm (AEFW) eggs, another polyclad flatworm species.
There is quite a bit of debate over whether gall crabs are reef safe, but I, personally, have not experienced any issues. The female builds a small hole in live rock, and corals grow around the crab. Since sick corals often contain gall crab inhabitants, the crabs are often blamed for the coral’s ill health. I should note that extremely large, healthy corals in the wild house gall crabs with no noticeable problems. The female shown is carrying eggs (in yellow).
Although sea spiders are certainly creepy and may have eight legs like land-dwelling spiders, sea spiders are only distantly related. The sea spiders identified here are more interested in eating coral than eating pods in a reef tank, which makes them all the more scary!
Acanthastrea-Eating Sea Spiders: Not Reef Safe
Here’s another one for your nightmares! For years I had heard rumors of a stealthy Acanthastrea predator, but I had yet to find one (to my relief.) A while back, I attended a coral fragging demonstration, and along with my frag freebie, I also received these lil buggers.
Rumor has it that these spiders tend to prefer Acanthastrea (typically called “acans”) corals, but they have also been found on other large polyp stony corals (LPS). Thankfully I eradicated these spiders before I had a chance to find out if they would infect my other LPS corals as well.
This Acan-eating spider shown below (hereafter referred to as AES) has (or had, I should say) eight legs. This is likely a female as the males have a specially modified leg (called an oviger) for carrying eggs (unless I knocked that leg off accidentally too) (Cowles, 2009). As you can see, there is practically no body – it is mostly legs. On the left side of the AES in the photo are the chelicerae (mouth parts) and the proboscis (tubular mouth part for ingestion). As mentioned – these are not true spiders! (Although they still give me the heebie jeebies!)
Acanthastrea-Eating Spider
How to Identify AES:
AES are nearly colorless, so they blend in quite well with the coral. Even after a thorough visual inspection of the coral prior to dipping, I only found these after they fell off in the dip. The ones I found were about 1 cm in diameter (nearly half an inch). So, I recommend a good coral dip prior to introducing the coral into your tank. As they can rapidly eat Acanthastrea corals, proper identification of sea spiders is critical.
How to Treat AES:
Various dips may be effective against AES; however, multiple dips may be required to eliminate any recently-hatched eggs (most dips are not effective on marine pest eggs).
Hydrogen peroxide dip: This is my preferred method for AES. This dip creates bubbles that will actually lift the AES off the coral – they usually can’t hold on! Use this dip with caution as overdoing it can cause serious coral damage. Also, only dip LPS in it. Soft corals and small polyp stony (SPS) corals do not typically respond well.
CoralRx, Lugols, and other commercially-available dips: Although I haven’t used these dips on AES, they should work…possibly with varying levels of effectiveness. Several brands tout effectiveness against pycnogonida (sea spiders).
Natural predators: Certain wrasses and other typical pod-eating-vertebrates may eat AES, but I’m not aware of any definite natural controls.
Manual removal: If your eyes are good enough (or are helped with a magnifying glass), you may be able to manually remove AES with tweezers or a pick. However, you may miss some and end up with a worse problem down the road.
Other: I am not aware of any in-tank treatments (other than possible natural predators). Additionally, Bayer insecticide is a common hobbyist treatment for marine pests; however, it was not designed for reef usage. Please read the label.
AES Conclusion:
Although Acanthastrea-Eating Spiders are quite creepy-looking, they are not a horrible pest to eradicate. They are highly susceptible to coral dips and can even be manually removed. If you know you have AES, please be a responsible reefkeeper and do not pass your coral on without at least notifying the new owner.
Note how different the AES above is from the Zoanthid-Eating Spider (ZES) shown below. The AES is much larger and has a much smaller (proportionally) body. Both have eight legs.
The photo below is of a zoanthid-eating spider that came off a zoanthid colony during a dip in CoralRx. It is in a water droplet on the top of a water test card for size reference.
Zoanthid-Eating Spider
How to Identify ZES:
ZES are extremely tiny, so they hide quite well in the coral. And, they are able to attach themselves very well inside the zoathid polyp. Even after a thorough visual inspection of the coral prior to dipping, I only found these after they fell off in the dip. The ones I found were about 3-5mm in diameter. So, I recommend a good coral dip prior to introducing the coral into your tank. Since they can devour Zoanthid corals, proper identification of sea spiders is critical.
How to Treat ZES:
Various dips may be effective against ZES; however, multiple dips may be required to eliminate any recently-hatched eggs (most dips are not effective on marine pest eggs).
Hydrogen peroxide dip: This is not an ideal treatment for ZES, as soft corals (zoanthids) do not typically respond well.
CoralRx, Lugols, and other commercially-available dips: These ZES photos were taken after removal with CoralRx, so these preparations may have varying degrees of effectiveness based on brand/solution.
Natural predators: Certain wrasses and other typical pod-eating-vertebrates may eat ZES, but I’m not aware of any definite natural controls.
Manual removal: If your eyes are good enough (or are helped with a magnifying glass), you may be able to manually remove ZES with tweezers or a pick. However, you may miss some and end up with a worse problem down the road.
Other: I am not aware of any in-tank treatments (other than possible natural predators). Additionally, Bayer insecticide is a common hobbyist treatment for marine pests; however, it was not designed for reef usage. Please read and follow the label.
Zoanthid-Eating Sea Spiders Conclusion:
Although Zoathid-Eating sea spiders are quite creepy-looking, they are not a horrible pest to eradicate. They are highly susceptible to coral dips and can even be manually removed. If you know you have AES, please be a responsible reefkeeper and do not pass your coral on without at least notifying the new owner.
“I’ll just feed my tanks before bed.” Famous last words. I spent the next two hours with a microscope and the glow of my computer screen instead of my nice, cozy bed. Even then, it took quite a while to find someone to identify them as likely the cercariae stage of fluke parasites in my reef tank.
A few minutes after feeding my reef tank, I noticed some rather large “pods” swarming around the top of the still water (all pumps were in “Feed Mode” – off). Odd, but nothing too weird. After all, I thought they were Ostracods at first (seed shrimp). On second glance, they looked too big. I paused, and then I realized what really caught my eye. They were red. Other than “red bugs” (Tegastes acroporanus), I’ve never seen red pods. I sighed in hesitation, then accepted my fate. Bed would have to wait.
I took a sample. There was no doubt; these were truly red. Ok, red Ostracods, right? I wouldn’t have to get out my microscope and prepare a slide, right? Wait. Ostracods don’t have tails. Noooooo.
Up Close with a Microscope: Fluke Parasites
I prepared a slide, and nothing could have prepared me for what I would find. I expected something in the definitive worm or pod realm. But not this. This was respiring. It was opening and closing its… mouth?
Closed…Opened…
Close-up of its anatomy… for what it’s worth.
Up until this point, they looked all cute. Like, little swimming strawberries, right? Nooooope. More like Sauron’s Eye (check out the video below).
So what are they? I have no idea. Every idea leads me down the wrong path. The closest I’ve landed is maybe some sort of larval sponge? (See update below.)
Identification: Fluke Parasites
Update (12/27/2020): Thanks to Reeffraff on Reef2Reef back in July 2020, it appears these are likely the cercariae of a trematode or fluke (in other words, they’re likely parasitic). Their life cycle probably involves snails and fish. I was right: these fluke parasites in my reef tank were the thing of nightmares! My treatment was to run fishless for several months (as the snails can shed for weeks/months). Another option, which I did not utilize, was to run PraziPro. I decided against that approach, as the number of worms (e.g., spaghetti, bristle) in my tank would probably cause a crash. I plan to quarantine all future snail purchases in a fishless system to avoid these.
