In my opinion, a cleanup crew is something you may want, but you certainly don't need one.
I have 9 tanks totaling 850g plus related sumps and I have no "cleanup crew" as such. Three tanks have a serpent star and two tanks have blood shrimp and cleaner shrimp, and there are miniature snails and some miniature limpets growing in some of the systems from the live rock, (They never grow larger and are slightly smaller than the end of a pencil eraser) but I don't add snails and hermits. I prefer doing whatever housekeeping necessary to avoid getting these critters that seem to die off in great numbers in many hobbyists (and LFS
When I am going to do a water change and cleaning, I let the algae build up a little on the glass so I can wipe it down, let it settle, and vacuum it out. Oh yes, I forgot. Before I vacuum, I also blow off the rocks with a power head and let the detritus settle and vacuum this detritus as well as the wiped off algae out of the tank.
A ninety gallon tank takes about 30 minutes not counting the settlement time for the algae and detritus, once a month, taking out 20g and replacing with 20g new salt water.