I bought one couple of month ago. I think they are very inteligent and adapt quicker than any corals or nems. I even managed to target feed mine without it freaking out.
But let me tell you something., my brother's tank crashed and all his corals and fish died one after another. Water prams were all spot on. I suspect his sea apple died and poisoned his whole tank, again its just a guess. Im keeping a close eye on this one, the first sign of decay and its out. If I manage to keep this one for 6 month i will be getting a yellow sea cucumber too.