We have a 65 gal freshwater acrylic tank with 3 filtration systems, charcoal, sponge and bio-media balls that are in the back of the tank. Is the charcoal necessary. I have no problems with ammonia and the pH level is sometimes off, which I correct. So far, the fish have done well (over a year). Also, if the charcoal is necessary, what is the easiest way to clean it? I appreciate any help or suggestions you may have for using charcoal. Thanks