rdnelson99
Aquarium Advice Addict
His is the biggest critter like this that I have seen so far. These two pics were taken back to back. Just 30 seconds before he stretched oxford the rock and was about 1/2" long and 1/4" wide.
I think they are stomatella varia. I found one in kind of a dormant "please act like you don't see me" phase in my tank and thought it was a limpet at first. Then I saw it again moving. I thought it might be a nudibranch at first, but found a pic online. They can move pretty quick if they want to. They are supposed to be harmless scavengers.
that is a stomatella snail.