I'm familiar with the keyhole Limpet, I actually got one cruising my tank now, but I found this one today.... Sorry about the pic, it's pretty bad... It's a little over 1/4" when flattened out, and when poked at displays a white slit.... freaked out when I flashed my flashlight at it thinking it was a nudi... I'm thinking some kind of Limpet, this critter reef safe? Thanks...