Good for sure. Consider your self lucky. Limpets are a great addition to any reef tank. They are sensitive to high nitrates and coppers, so having them absolutly tells you your levels are good. They are great for algea control as well. Leave him be, I have a fairly large one that makes an appearence about once a day, hes very cool to watch. They remind me of a cross between a slug and a mollusk, in the half shell that is!