Some thing is living on my live rock

[Brandontqm]

I just got a new tank a 15 gallon and took a pice of like rock out of my old 10 gallon tank to help with the cycling of the new tank. When I put it in I noticed what looked to be some kind of nim I just what to know what kind and if it is good or bad to be in my tank

 

[TommyP]

Looks like aiptasia heres a good read

Aiptasia Anemone - Information and Control Methods

 

[Sniperhank]

I'm going to put my money on hydroids. Google it and see if that is what you have.