Depends what's in the tank....cleanup crews are kind of specific to each tank and what it needs. I would not buy more than about 10 hermits, and nothing aside from scarlet reef hermits for a reef...my opinion. A single fighting conch will do wonders for the sandbed, and probably about 18-20 astreas for the glass....the actual number depends on the rocks, but they often migrate to the glass anyway.
30 astreas, 10 scarlet reef hermits, 10 ceriths, 1 fighting conch (must have), 2 emerald crabs, a sallylightfoot, and lots of worms.
There is a big difference in the aggressive nature of female or male sallys, and I am struggling to remember how to know the difference....I know you have to flip them over and check the bottom shape......anyone?? One is "V" shaped, the other rounded or something.....????? anyone know?
Just about any blueleg hermit you buy will already be in an astrea shell....they love them, but scarlets prefer a different shaped shell.....yes, they will use astrea shells, but only if they have to, so astreas/turbos are great with scarlet reef hermits which are just about the least aggressive hermit...cost a little more, but a much better choice.
Just my thoughts.