Well I know most on here aren't big fans of crabs. I like to have a few, but rely mainly on snails. You could have a 100 little snails or like 2 or 3 dozen good sized turbos. I overstocked my tank at first when I had a lot of algae and when the algae cleared up the crew slowly died off until I hit the right amount. One thing I would say is that the packages they sell online at places seem to be way to much. In my 75 I have 3 starfish (green brittle, red brittle, and orange linkia) , 2 shrimps (cleaner and Coral banded), about 12 blue leg hermits, and like 12 turbos (including 2 giant ones), as well as a few misc small snails. I used to have some nassarius snails, I like them a lot, but one of my gobies hunts and kills them. Even with heavy feeding this small crew has kept my tank spotless for 3 years since my algae was gone. Previous to that I had like 100 members, but as I said when the algae got cleared up they slowly died off. Hope this helps.
As for a cleanup crew, in all honesty, I'd wait until the tank has cycled and all traces of ammonia and nitrite have dropped off. You don't necessarily want to expose them to it so it would be best to wait it out a bit and just keep testing your parameters in the meantime. As for what to add, it all depends. Some people like hermits, some like snails, some like a combination of the two, and then there are those that like to add in some brittle stars etc into the mix, but all a personal preference. You will just need to make sure you have a sufficient food source in the tank to keep them fed. Just a thought...Good luck
