just have lots of plants and moss. be careful as some fish will eat moss. if i was you i would pu in an asian fan shrimp. there kool to look at and are filter feeders.
If you want fish, go with one of the "nano" fish like Dwarf Rasboras, I know someone that keeps them with CRS without problem. For shrimp, any shrimp should do as long as there is enough of a food source.