Depends on your bioload (how many fish you have) and what other if any filtration do you have (Live rock, skimmer). I started out with biowheels on my Penguin 330 power filters and after the tank established itself and I added LR and DSB I took the biowheels off and just use the filter for circulation and a way to run carbon once a month. If you have a healthy amount of LR (1lb to 1.5lb per gallon of water) then you won't need the biowheel unless you overstock the tank with fish.