Looks like the same kind of little pest I get on new corals now & then, a SeaChem dip makes em jump off and die and I rinse them down the sink

Don't know what they are called exactly, but I have always assumed they were "Bad". If you have one, it probably came in as a hitchhiker on a coral, you there is a good chance you have more.

I dip EVERYTHING (ok, not fish ;)) in SeaChem before it goes in the tank!