Critter ID Help

[kelloggreef]

I found a critter on my rocks that looks just like a snail but with no shell. It seems to be forming one on it's back, it is hard and comes to a point, but looks to be the color of it's flesh. When I put it in a tupperware and look at it from the bottom it looks just like a snail on the glass does. Are snails born without shells? I don't want to sound stupid but I also don't want something bad in my tank. I tried to get a picture but they were all so blurry.

 

[budsreef]

Sounds like Stomatella, which is a common hitchhiker and ok to leave in the tank.

 

[kelloggreef]

Looked it up on some internet site and that is exactly what it looks like.
Thank you so much!