Banded trochus if you can find 'em and are willing to do a slow acclimation if your parameters are too different. Dwarf polka-dot hermits (looks like a mutant scarlet reef hermit) are great for general clean-up - mine never stops eating.
Those are my preferences given that if one dies it doesn't nuke your tank. Lettuce nudis are awesome at dealing with several byropsis variants, but I haven't had good luck keeping them long-term... the either starve once they've eaten the offending stuff, or crawl into powerheads/out of the tank.
