I don't know about biowheels, but I'd think it's a matter of how the fish eat. I have a powerhead filter which causes the pellets and flakes to sink quickly, but I don't turn it off. 2 of my 3 cherry barbs are very aggressive when it comes to food, and will fight over the floating food, but the 3rd is more shy, but will immediatly grab anything that sinks. If the filter is causing food to sink and it's ignored and gets lost in the gravel, then it's probably a good idea to turn off the filter when feeding, but if everything is being eaten, it probably doesn't matter.