I've got a 10 gallon that I'm breeding Red Cherry Shrimp in. All I'm using is a sponge filter rated for a 40 gallon tank. Two 10 watt bulbs and a host of live plants. I'm using Fluval Shrimp substraight. Anyways every week I tend to find new critters running around the tank. First it was a bunch of somethings that resembaled a mite, just a white speck less than a MM in size that would bounce around all over the place. Then I had a bunch of white to light brown "centapeeds" about 1 MM to 4 MM in length crawling around everything. And lastly I have some sort of worm, that looks much like an brown earthworm about 1/2 to 1 1/2 inches long bredding like crazy in the substraight. They are kinda cool since they like to poke what I assume is their heads out of the dirt about 1/3 their body lenth and hang out for a while until something scares them back under. I don't know if any of these are really bad for the system. I put some Assasin Snail in the tank and it seemed to cut back on all three a bit. Does anyone know what the heck all these critters are? Or where I can go to find out? I know a picture is worth a thousand words but I would need a much better camera than I have to capture them.