I had some sort of algae on my glass, not sure what type. Regular aquarium snails (ramshorn mini ramshorn, mts, pond, bladder) would occasionally nibble on it, but never made much of a dent.
I got a pair of nerites (10gallon), and they cleaned it up within the week, and they've kept it clean since.
For what it's worth, I think my tank is on something like 4 on, 5 off, 5 on currently. not sure if it was the same initially.