Anyone Know What This Is??

[TVR]

Originally Posted by Tarolisol

im pretty sure its a keyhole limpet. sometimes it will have a white patch on its back. They are harmless.

If so, thanks for both the question and the answer - Because I have 2 of those hickhike with the rock when I bought some corals last month. I was really small and now almost about 1/2 inches. Still in there