Shrimp don't really stir up the sand at the bottom, but they are interesting creatures to keep, have a look around at your local fish shops (lfs) and see what choices you have. Ghost shrimp are nice, but they are also opportunists and if one of your fish if sick etc they will eat it (as will most shrimp and other fish) others you can get are filter feeders - you can tell these as they usually have "fans" at the end of their front legs, these are totally harmless to your fish, but they won't really eat the debris at the bottom of the tank. If you like ghost shrimp, go for it, they are interesting, remember you will need to cycle the tank before you can put in inverts, they need good quality water to live happily.