Well it also depends upon what other animals are in the tank. Many fish will prey upon them and you'll not be able to keep any. If you are going mainly for an invert only tank, very cool, then I'd bet you could get away with a whole lot. Somewhere between 50-100. But if you keep that coral banded expect to only have 1 shrimp. Coral banded will tear apart other shrimps.
Good shrimps, fire (blood), peppermint, cleaners, camel, sexy, harlequins (if you don't mind feeding them a live starfish from time to time). Harlequins are neat little creatures. Toss in a chocolate star and they will hunt it down. When they get to it they will slowly eat away one leg at a time over the course of about a week.