They are a fresh water shrimp that feed on algae, dead plants and just about anything else. They make excellent scavengers, and are completly unagressive, even with fry as small as one day old livebearers. Some fish however will try to eat the shrimp, or pick at them. But surprisingly a lot of the smaller types of fish will co-exist with them very well. 
 
The shrimp are quite vunerable during their molting. That's when they cast off their hard shell covering that has become too small and emerge with a shiny new set of armor, and a little bit bigger. The new shell takes a few hours, up to a day, to harden, so you'll need to supply some hiding places for the shrimp to use during this stage. From time to time you might see the old empty shells lying around. Don't be alarmed, now you know it's just an old shell and your shrimp is growing. 
 
Ghost Shrimp will eat any kind of fish food, they especially like left-overs. As long as the water is clean they will just about take care of their selves and if you're lucky they might lay some eggs for you. Shrimp that are carrying eggs are easy to spot, the eggs are green and you can see them thru the transparent body. The babies are very tiny and extremely hard to raise artificially. You'll have better luck raising them outside during the Summer in an old barrel or kiddie pool.