I don't have an ro/di unit at the moment. I've noticed a diatom bloom shortly after a water change. I use a single DI filter from aquarium pharmaceuticals. Obviously it's not working very well or doesn't last very long. Anyways I'm wondering if I added my mag350 canister filter to the mixing bucket filled with a phosphate sponge and allowed it to run for 24-48hr would this help eliminate the po4.