you have to remember, fish poop out almost as much as they eat.. a fish you add as a cleaner will just produce more waste, making your tank dirtier.. it doesn't matter what kind of fish it is. Slight exception with some plecos as their waste doesn't degrade as quickly or easily, keeping it from turning into small, rotten particulates trapped in the substrate.
If you need a fish just to get stuff off the bottom, the striped raphael does a decent job.. but only at night. If you wake up the next morning and have food at the bottom, then a striped raphael is perfect. It deosn't matter what I throw in my tank, it's always gone the next morning.