I have a ~130 gallon freshwater tank (72 x 19 x 24) with two Aquaclear 110s and a Penguin 350. My idea is to go carbonless on the tank, and replace carbon with bio-balls on all filters. I have read around here and see a lot of advocation for replacing carbon with bio-balls on the Aquaclear 110. I'm thinking about doing the same on the Penguin 350. Basically taking the carbon sleeves out and filling up both sides with bio-balls instead. I'm not going to get rid of the bio-wheels though. Just wondering if anyone has ever done this and if anyone can foresee any problems with this setup. Also, should I put the bio-balls into some sort of nylon stocking or bio-bag? I'm open to any ideas that would allow me to make better use of this piece of crap Marineland filter without having to change the carbon every month.