It depends on what you want. I agree on adding them to a more established tank, as I learned with my peppermint shrimp (rip Benjamin, died of high nitrates) but peppermint shrimp eat aiptaisa, but can eat zoas if they get hungry. Cleaner shrimp will eat parasites, mucus, and dead skin off fish. The pistol shrimp doesn’t really do anything. The coral banded is a good scavenger, but will eat other shrimp and small fish. You can not keep shrimp with triggerfish, puffers, some squirrelfish, lionfish, and fish that are not invertebrate safe