I just bought a new 75 Gallon Tank that came with an Emporer 400 HOB filter. It has been running for a few days with 15 guppies in it. It has 4 media compartments. 2 have cartridges that I cut open to remove the carbon and I stuffed 1 with a floss pad from an established canister. I also have 2 media "baskets/cartridges" that are filled with ceramic rings from an established canister. Emperor seems to be good enough as far as mechanic filtration is concerned, some I would like an additional filter to help out with bio filtrations. What would be a good option? I'm a little strapped for cash. I was thinking about adding an Aquaclear 70 loaded with only bio media. Do you think that would be sufficient? If not what else would work. My budget is about $50.