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Challenges of Reef Keeping – Zooanthid Eating Nudibranchs

This week I would like to take a look at another annoying pest in the reef tank, the zoanthid eating nudibranch.  The zoanthid eating nudibranch is much like the soft coral eating nudibranch in both body shape and difficulty to find and eliminate.  The zoanthid eaters usually belongs to the famliy Aeolidia.  They are built much the same as the soft coral eating nudibranch, with cerata or finger-like growths that grow on their dorsal side.  These growths allow them to blend with the zoanthids, making them difficult to see as they feed on your polyps.  These nudis are usually small, ranging in size from 1 millimeter to 1 centimeter in length, which also makes them very difficult to detect and remove from polyp colonies.  They tend to hang on to the underside of the polyp and remain hidden. 

A good time to look for zoanthid eating nudibranchs is right after the lights turn on, while the polyps are still closed.  Usually this is when you can find the nudibranchs along the shaft or base of the polyp.  Once you’ve determined that you have these pests, extract as many of the adults as possible with a small pipette. This will help to keep the population in check, along with regular dipping in Lugol’s Solution or Coral Rx. The eggs and egg-cases are another problem.  The egg casings can be seen upon inspection of the polyps, usually right under the polyp head or on the body of the polyp.  These egg casings can be pulled off gently with a pair of tweezers and sucked up with a pipette. 

These creatures can be even harder and more annoying to take care of than the soft coral eating nudibranchs and require much more patience when trying to get rid of them. Since polyps grow very closely together finding and destroying these reef pests can be an involved project The best way to help prevent these animals from infesting your tank is to quarantine all new coral and treat each piece before placing them in your show tank.  Treatments may take at least 2 weeks to kill the adults and allow the eggs to hatch.  Once the eggs hatch, continue treatment to try and fully eradicate the newly hatched offspring before they mature and are able to begin the reproductive cycle again.  Precaution and patience will get your tank back on track if you ever have an encounter with these pesky and destructive slugs. 

Best of luck,


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