Nocturnal species ID

In my newly set-up (8/2/09) and near complete cycling 14g nano I've noticed a couple of snail/like like creatures cruising the glass when the lights aren't on. Its hard to tell for sure but it seems like they may have a very small and relativley flat shell/exoskeleton that is very well camoflauged with the rest of the body. Without a pic can anyone tell me what they might be and if they are safe? When I turn the tank lights on they me a bee-line, as fast as slugs/snails are capable, down the glass and into the comfort of the liverock. I began seeing this about 10 days ago and then then the other night I noticed two of them on the glass/acrylic another one along with a very, very small (3-4mm) "thing" shaped just like a limpet. I also spotted a 2cm bristleoworm cruising the LR the other day as well. Seems like I have lots of activity - just want to make sure these are keepers and not pests.

Thanks

 

probably a harmless stomatella snail stomatella - Google Images

 

LOL

Great minds think alike

 

Yep - that's them! Based on the description of the first image I clicked on it seems like they are good reef critters. What about the tiny limpet like cruiser?