Sponges -how toxic

[euromomtx]

I was thinking of adding a few sponges to my tank but was wondering what the risk was of them harming my other animals in the tank. I read sponges can be very toxic.

 

[Elysia]

I believe that a lot of sponges contain distasteful or toxic chemicals to help ward of predation -- remember, out in the ocean there are all those angelfish that feed on sponges. I do not think that most sponges are toxic in the sense of the "sea apples" (Pseudocolochirus spp.), which can release the toxin holothurin if stressed and potentially kill fish tankmates.