As long as the biowheels are spinning freely at any speed, they should not cause "nitrate buildup." Biowheels are not like bioballs; they do not have enough surface area to trap the amount of debris associated with nitrate buildup in bioball trickle filters. As it is, filters like a biowheel (and bioballs, really) are
supposed to generate nitrates: that's their goal. Biowheels are aerobic filters for the more common oxygen-loving bacteria nitrosomonas and nitrobacter to bind to and metabolize ammonia into nitrite and nitrite into nitrate. The bacteria that commonly metabolize nitrate into safer free nitrogen are mostly anaerobic critters that are not found in any great numbers on the biowheels. That's where your live rock comes in; the deep areas of the rock are great places for anaerobic filtering potential.
I think before we go further we should find out what kind of algae bloom you're looking at, and what other parameters the tank has. Is it hair algae? Slime (cyanobacteria)? Red turf algae? I'd also be curious about what kind of flow your tank has, what the lighting is, how old the bulbs are, and how much you're feeding. Questions, questions, questions.......
