Is this Daphia or other kind of critter?

I took 2 pictures of the critter I think it might be daphia, I'm clueless about tiny critter. Here's the story... I have this 5 gallon bucket with playsand, and some tiny MTS. Today I noticed that there were some kind of floating critter that swims around in the water. Kind of cool to watch. I thought that it might be Daphia but I would like to confirm this so I tried to take some pictures, those 2 are the best as I can get.

http://img360.imageshack.us/my.php?image=thing9ed.jpg
http://img360.imageshack.us/my.php?image=thing16ny.jpg

I dont think they can be tiny MTS because they swims in midwater, almost like zipping around on their own way. Its really tiny, like specks of dirt. Oh, the bucket is unfiltered and unheated if you wanted to know.
Any ideas?

Ah, thats neat. I've looked up ostracods via google... it would be helpful if I had microscope huh lol.
Now I'm curious... are they good for anything? Should I keep trying to grow more of them or don't sweat it?
Gee, I'm a geek ain't I? :joke:

SubLime, I knew it that I could count on you chiming in!