Jellyfish!?!?!?!?!

[justinl]

well... technically any crustacean larvae are called nauplii tony

hydroids and cnidarians can have what is known as a medusa stage. the medusa looks like what most people know as a jelly; hydroid medusae are called hydromedusae and look very similar but have a few mostly anatomical differences. All of them have a polyp stage. medusae are supposed to settle and make a new polyp but I highly doubt that they can accomplish this in captivity unless special precautions are taken.

in the end though the result is the same; it will get eaten or chopped in a pump, either way it will die without causing any harm.