just take the rock out the tank and scrape it off. use a screwdriver or file and scape some rock off too so you dont have residue. they use a spray bottle to spray off the rock with saltwater to wash any left off. No matter once you see one they will keep coming back. If your water quality is good thats all you'll get a bubble here and there really not requiring any action. if your water quality is poor (high nutrients) then they will pop up all over the damn place quickly.