What In The World Are These, And Can I Keep Them In My Aquarium?

Hello everybody, I recently collected some very strange-looking invertebrates and was wondering WHAT IN THE WORLD THEY ARE and if they would be okay to put in my aquarium. I can't post a picture right now, maybe I can get one later, but here's a description:

Small, three-quarters-of-an-inch-long creatures that look like centipedes with pinkish-red gills at the end of their tails, whitish/translucent bodies, hardly visible eyes, and lots of legs. One rolled over to clean it's legs/gills so I assume they are tidy creatures to some degree. I fed them some snail jello and I'll try to get a picture soon. My tank has fish, snails, and plants- would they harm anything?


Thank you!

 

So here are a couple pictures, sorry for the bad resolution. Can you tell what these things are?

 

Looks like some type of amphipod?

Don't think they'd harm anything but I wouldn't know for sure. Don't think I've ever seen them in aquariums before. Cool looking critter though!

 

Where did you find them?

 

Looks like scuds. In which case they are find to keep, a good food source for your fish.

Edit: They will eat live plants. So if your fish aren't eating them you might not want to keep them in a planted tank.