We have these in the Atlantic along Daytona Beach. They are in the Halifax River that empties into Ponce Inlet, then to the Atlantic. I have had them in many tanks that I keep as "local" tanks. They will eat by filter feeding like most anemones in the wild. Since they only come out at night, as long as it is not large enough for a disabled small fish to enter it, the fish should be fine....if it's the same things I have here.