I haven't changed the carbon in my HOB filters in a very long time. I usually just rinse them out every once in a while to just clean the waste out. The carbon is probably doing nothing because its probably inactive by now. My fish are doing just fine and looking and feeling great so I was starting to wonder is carbon really necessary? Or am I doing something horrible to my fish by not changing it? What do you guys think because I obviously don't want to harm my fish in any way and I want them as healthy as possible.