I have these things in my tank....

I was cleaning the glass and noticed a lot of these little critters on the glass near the substrate. My camera with the macro setting has a dead battery, but I'm not sure if I could get a pic anyway because they are so small. The are kinda oval shaped, with what looks like to be 10 or so legs, maybe two antennae, and they crawl on the glass and substrate. Their bodies are clearish and the largest of these things seems to be close to 2 or 3mm, while the smallest are about the size of a period (.). I can try and get a picture later when my battery is charged....
Any ideas what these critters might be?
Thanks!!
Robbie

Thanks for the quick reply...just for my own piece of mind, here are a couple of pics.
My glass is really not as dirty as it looks, btw. Well, it is down close to the substrate where these things are hanging out.
I keep it clean! I swear!
Thanks!
Robbie

Thanks guys!!!
Robbie