I'm not an expert at anything, but after 11 yrs in the hobby as of this month, and having 7 systems totaling 850g plus sumps, I find it odd to see posts about clean up crews, as though they are a needed part of the hobby.
It wouldn't be so bad if one only had them because they liked them, but some seem to think they are a necessity in their systems.
Over the years, I've had my share of algae problems, but, after fixing the cause, the algae went away.
I did buy a few hermits and snails when I first started, but the snails died, and the hermits seem to kill one another off, so I never got any more.
I notice at the fish stores, how many shells line the bottom of the tanks. It doesn't take long to start seeing them die off after a store gets a new shipment.
Numerous posts on many boards seem to indicate that this is a common problem with the hobby, yet people keep buying them.
I realize that there are hobbyists who keep them and don't have this problem so I assume the problem may lie with source or shipping and handling.
In view of the large fatalities of snails and hermits, why wouldn't one just fix the problem instead of trying to rely on something that many times dosen't have longevity?
I guess the closest things I have to be considered "cleanup crew" would be my cleaner and blood shrimps, and my serpent star fish.