5 gallon tanks are great for shrimp. You'd need a fully cycled filter (with a prefilter sponge over the intake) and a tank that is preferably somewhat mature (mature tanks have established growth of things like biofilm, algae, micro fauna, and other goodies shrimp eat). Depending on where you're at you may need a heater, but RCS do fine in cooler temps too. Live plants are always recommended, particularly moss. Shrimp do best in species tanks but it would be possible to have some nano fish with them too.