Lets all remember that all fish and inverts have common traits but don't always do them. I have to second that cuc are a bad idea in a small tank as the amount of toxin they can release when stressed or die. I once had a sea apple who died in a 150 and it didn;t kill anything, but this is because he died a normal death and was not being harrassed, but if he was he would of let the toxin out to kill everything around him just to make sure that if he was going out he was taking the predator with him.