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Dying Acropora Coral Rehabilitation
acropora
Black Bug and Gray Bug Acropora Parasites
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??)
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.
Dying Acropora Coral Rehabilitation
Back in 2012, I took in several corals from a fellow reefkeeper, knowing they were all rescues. Included in the bulk were a few dying Acropora corals that desperately needed rehabilitation. However, rehabilitating small polyp stony (SPS) corals has its own challenges, and in many cases, these sensitive corals may experience a more rapid death than their large polyp stony (LPS) counterparts. Below I will cover the initial inspection, diagnosis, treatment, for a complete dying Acropora coral rehabilitation.
Assessing Dying Coral Health:
All dying Acropora coral were brown, not extending polyps, and had white marks on them. Upon initial inspection (and not shockingly), they had red bugs (Tegastes acroporanus) and Acropora-eating flatworms (AEFW). I treated the AEFW and red bugs with a series of coral dips as part of rehabilitation efforts. I also inadvertently subjected the tank to a reduced temperature (thanks power outage), which quite possibly killed the red bugs. (At the time, Interceptor was the normal protocol for treating red bugs, but there were also several other suitable treatments.)
Since AEFW lay eggs, it was critical to regularly inspect the coral and re-treat to completely eliminate the parasites. Thankfully, red bugs are live-bearers, so once they were initially eliminated, I no longer had to worry about them.
Quarantined Acropora Coral:
Of course, Acroporas require stable salinity, alkalinity, magnesium, calcium, etc. Given that I had over 50 corals undergoing rehabilitation at the time, my quarantine tank was not exactly a healthy aquarium. I had to focus particularly hard to make sure the other dying corals did not adversely affect the SPS. Water changes to remove excess nutrients were crucial. Once the Acropora parasites were gone, I maintained my alkalinity at 9 dKH, magnesium at 1350, and calcium at 450. I also performed 20% weekly water changes.
Previously Dying Acropora Coral Rehabilitated:
With stable parameters and a lack of parasites, this previously dying Acropora coral was quickly rehabilitated. They can heal quickly and add a beautiful touch to the aquarium. However, I don’t recommend Acropora rescues for beginners as they can have more severe pests than LPS corals, are sensitive to poor water conditions, and require careful monitoring of water parameters.
Red Bug Parasites (Tegastes acroporanus)
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.
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!