These have started to take over my tank. They don't seem to be causing any trouble. The tank is 75 gallons and I've had it for almost 20 years with no new inhabitants in the last 10 years. Are these good or bad and what form of anemones are they?
They spread like wild fire or in my case, like oil grease when you're working on cars lol. They're almost ineradicable. If you don't mind how ugly they are or you don't plan on putting other corals in, you can simply just live with it. Other wise you'll have to kill the live rock by leaving in exposed to air. Some people say you can take care of it with predators but it never stops, they'll just keep reproducing.