burdundi wrote: Aiptasia. Get rid of it. You can use kalk paste and inject them with a syringe (Joe's Juice is the commercial version) or peppermint shrimp have worked for me. Some people don't have luck with peppermint shrimp, but they have always worked for me.
-Andy
If you are not running a reef tank, but are just running Marine fish and live rock, are they okay? I don't have any live corals etc.