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Originally Posted by askinz
...We've heard horror stories of entire tanks being wiped out after a sea cucumber died and released a toxin into the tank. Do sea hares release anything like that when they die? If so, what steps can we take to save the rest of the guys?
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It will depend on several factors, some of which will be unknowns for your system. Sea Hares are Opisthbranchs of the Order
Anaspidea, and their evolution from the torsed shells to shelless or internally shelled creatures is th ought to parallel the adoption of chemical defenses and attainment of secondary bilateral symmetry. For this order, the reduced shell is buried in the mantle (some spp. have no shell whatsoever). Although reduced in size, the mantle cavity and gill are still present, and the posterior edge of the mantle can still be rolled into an exhalent siphon.
The chemical defense of the Sea Hare is a purple dye associated with the red pigments extracted by the Hare when grazing on certain red algae (some spp. of cyanobacteria possibly as well?) they may feed on in the wild. Although the Sea Hare may release these dyes when disturbed, the toxicity is questionable, and may be more like the dye associated with some cephalopods (Octopi and squids) and be more of a camouflage and/or smoke screen to allow an escape or to confuse the potential attacker with an irritant. The absence of these red algae in a closed system will most likely prevent their dispersal of the purple dye as a potential toxin in your system anyway, and as a complex pigment, would be easily removed from the water column by skimming and appropriate use of active carbon. Although I cannot find documentation to support toxicity of the dye, it is reported that truly large specimens of
Aplysia spp may release enough toxin to be harmful to fishes (J. Spung's Invert book and a questionable reference in Anthony's Invert book).
Ron Shimek states (p 330 in his invert handbook) that there is no good reference on ANY toxicity to support the toxicity claims, and I cannot locate any reliable sources of toxicity info (the marine biology literature), but this is not to say that it
may exist. Regardless, this should not be an issue to most systems of corals, etc.
I don't think you have anything to worry about unless the Sea Hares came immediately into your system from the Ocean or is an extremely large specimen, even then I do not think it much of an issue. Just to be on the safe side, perform large percentage water changes for a few days, run fresh carbon, and jack up the skimmer to a
wet skimmate. I feel that this is one of those mythinformation issues that has been perpetuated in the hobby for some time, but again, better to be safe than sorry, so do the water changes and run the carbon and the skimmer.
Sorry to be so vague, HTH.
