Found this in the tank the other day, must of been attached to a coral or piece of live rock. Does anyone have any idea what it it is and whether or not it should be left in the tank? It is about an inch in length. Thanks!
Fishy is correct. It is a soft coral eating nudibranch. It will not eat other foods. Leather corals are its speciality. If you have these I would remove and destroy. If you want to keep this animal set up a Nano tank with leather coral frags from your main display tank. Just don't plumb the 2 systems together.