Can you ID these baby shrimp?

[Sagat]

While doing my daily inmate check, I saw a bunch of things wriggling around on top of my pool filter sand. At first I thought they were fleas or something nasty, but the more I look at them, the more they look like shrimp... except that I've never bought shrimp.

Could these have hitched a ride on the plants I bought at my LFS? They're really small (pond snails and grains of pool filter sand for reference), so it's hard for me to compare them to anything and come up with anything but 'baby shrimp'

[sayurasem]

It's a scud.

[ravensgate]

Those aren't shrimp, they look like scuds.

[Sagat]

Oh boy, fun. Time to do some research. Thanks!

[wicca27]

free live fish food lol

[Bananariot]

You can call them shrimp if you believe scuds are shrimp. They look like headless shrimp lol.....gammarus something.