Clean up crews on line are OK, just watch the numbers.
Stay away from cucumbers and nudebranchs. If they die and you don't notice right away, it can be trouble.
I think a good rule of thumb for cleanup should be bosed less on gallons of water and more on amount of rock, lighting, and bioload. If you have a lot of rock, but not too much light and a very low bioload, then you would need less hermits and snails than a person with high light and tons of fish to feed nitrate to the algae.
I would say 1 hermit and 1 snail for every 3 pounds of live rock. Less if they are large snails and hermits and less if you have other algae eaters and clean up critters.
I have a 72 gallon with just under 100 lbs of rock.
I use 25-30 hermits of assorted varieties. Scarlets, blue legs, zebras, a couple of green, one white one, 3 or 4 of these grey ones with red whiskers, and one neat purple one.
about 25-30 turbo snails
2 trochus snails
2 bumblebee snails
4 queen conchs
1 fighting conch
2 cleaner shrimp
You might wonder about the conchs and why I have so many. Never get multiple fighting conchs, because they need a good territory of sand to burry in and find food. I don't think my tank could support more than one. The Queens are just glorified snails and they spend most of their time eating algae off the glass and rocks. I was able to get them for $2 a piece so I got 4, planning to sell them when they get too big to eat enough in my tank. They get to be pretty big, but they grow very slowly, so unfortunately, your odds of raising one to be a foot long are very slim.
IMO, it's better to add less hermits and snails and then increase the number if they can't keep up with your system than it is to buy too many and have them starving and eating eachother. Personally, if it looks like there isn't enough algae growing to feed everyone, I feed the hermits, which also causes more algae because of the extra nutrients...there's ususally plenty of algae though. :roll: