Are they the true algae eaters or the false ones? The true ones only eat algae in their younger years but lose a taste for it as they age. A good thing you plan to rehome them.
I suggest ancistrus (commonly called bristlenoses. Make sure someone doesn't sell you a plecostomus by claiming it is a bristlenose!) as good algae nibblers but, like all fish, they don't always like all types of algae. Personally I have never found any fish that liked the black fluffy algae.