Can someone help ID this?

[causeidm]

Ok, I noticed a couple little balls on the sand next to the glass this morning. I figured they were just left over food or something that had collected there. I used some tongs to take one out and put it inside of a small cup. Suddenly the ball fell apart, it was actually about 50 very small creatures all bundeled together. they are small, about a mm in diameter, flat, and they have 2 little black marks on their back. I haven't been able to ID them att all, I have looked all over the web and through all of my books.
Thank you

 

[causeidm]

they are all tan in color, with those 2 black marks on their back, and its funny when they swim in the cup, cause they swim up then flip over and kinda fall side to side like a leaf. it almost looks like a flake of sand falling. They have tons of tiny little legs. I just worry if they are predators or not, I got all the ones that I could see, about 200 in this cup.

 

[clarkiiboi]

I dont have the answer, but curious. At first when you said flat, I thought flatworms. Then you stated tiny legs, so that threw me. I honestly dont know what could ball up and taken out of the tank without falling "apart". Bump for ya.

 

[causeidm]

Yeah, they are really freaking me out, cause now that they have been in a bottle together overnight, they have piled together in one big ball. I have never seen things like this in my tank, but I thought I read an article about them a year or so ago. I have had no luck id'ing them yet though. They have a really hard outer shell and they seem to really like balling up together, cause even when I picked them up with tongs, they stayed together.
I would take a picture, but I don't have anything that can zoom in that close. Maybe I can get one of the ball though.

 

[maximus42]

ill beleive that when i see it