It took four months for my 20 gallon tank to cycle . I purchased a seeded sponge filter from Angels Plus which seemed to help. I have an aqeon filter as well. My question is, shoUld I co to use to run the sponge filter as well as my aqeon? How soon is it ok to change the cartridge in the aqueon and how long should I leave the sponge filter in before I replace it?