Snail?

[Todd_elb]

Does anyone know what these may be. I have noticed them on the glass. If better picture is needed will try to one but these are the best 2 pics I have been able to get.

 

[cngh]

Hard to say for sure, but based in those pics it looks like a collonista snail. They get to 2-3mm in size, graze on algae, are more active during lights out. Collonista are good guys, but are small enough to gum up pump intakes and pre filters.