Mystery animal

[sketch804]

I don't know where to post this so I figured here because it deals with small animals. Anyway, I have these in a glass jar that doesn't connect to anything, and I just discovered them in my shrimp tank. Now I don't believe that these are harmful any in way due to my shrimp population exploding! They are small, clear, have antennas, zoom around on the floor and they can propel themselves through the water. they are too small for my eyes to focus on (even though I am youngish), but these images are the best I can get.

On the pix you can see the have shells they shed like other inverts. Any clue??

Oh the lighter items in the pix are the shredded shells not the animal.




So there you go, I cannot probably get a better picture than this.

Thanks!