Can anyone ID?

[awin08]

I was doing my standard night rounds before bed and saw this thing on my rock. Moving almost like a slug? Before I could get my camera out it hid into a hole so I couldn't get a clear photo ...

Whitish bottom with a brownish/red back? It was probably about a pinky nail size.

Any ideas?

 

[StartingATank]

Hard to tell by pic, but my guess is a stomatella snail if it looks like a slug. It will have a plate like shell on its back that looks like a fingernail. A very good CUC. I have some in my tank and they are pigs. I would say they eat about their body weight in algae.