I have a fairly new tank with two HOB's on it both came with carbon packs. I have switch out the carbon for more bio media and things seem to be fine. The cool thing is I have the Fluval C4 power filters and the come with a nifty little media basket so I didn't need to put the bio media in a bag....
55gal. Planted Freshwater tank, 2x Fluval HOB C4 power filters, 48" T-5 Fluorescent Fixture with a 54w 10,000k daylight & 54w Actinic light 3 Gouramis, 1 Cory Cat. 10 Tedras & 3 Angels.