Super Tiny Creatures On My Acquarium Sides?

[mrtiddles]

In the dark, if I turn on my aquarium light and look super close, I can see little super-tiny bits of 'debris' that are obviously creatures because of the way they move. You have to be almost eye-on-the-glass to see them, and they are definitely microscopic, but they also definitely move. Any ideas?

 

[Corleone]

Do they look like very small white or transparent worms? They're likely planaria, which are harmless, but an abundance of them usually means overfeeding or otherwise an excess of available food.