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.
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.
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.
Juvenile Berghia Nudibranchs:
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 |
[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.
References:
- Carroll, David & Kempf, Stephen, “Laboratory Culture of the Aeolid Nudibranch Berghia verrucicornis (Mollusca, Opisthobranchia): Some Aspects of Its Development and Life History,” Biological Bulletin, 1990. https://www.researchgate.net/publication/237641285_Laboratory_Culture_of_the_Aeolid_Nudibranch_Berghia_verrucicornis_Mollusca_Opisthobranchia_Some_Aspects_of_Its_Development_and_Life_History
- 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
- “Aeolidiella stephanieae, Valdes, 2005,” The Sea Slug Forum, http://seaslugforum.net/find/aeolstep, accessed 21 February 2022.
- ReefTown, Your Source for Berghia Nudibranchs, https://reeftown.com/, accessed 21 February 2022.