it all depends on how much lr you have, and how much bioload in your tank. if you have plenty of lr, and your tank isn't overstocked, then the wheels should be removed. on my fowlr tank, i have just enough lr to make the tank look good, and have a high bioload,- so i do use an emperor 400 with the biowheels and protein skimmer. It's been about a year and no problem. With regular water change, you shouldn't have any nitrate problems at all. and if you removed them, only remove 1 biowheel at a time. good luck