i believe that hith is brought on be poor water conditions. i do weekly water changes and that along with a good diet i've never had the desease in any of my tanks, knock on wood. i too have heard of the carbon theory but i've used them for years and still do. Cardon packs for my tanks are expensive so if i could get away with not using them i'd really like that. stay on top of your water changes and make sure the fish is in the proper tank size.
feed the fish's plane no sauce plz!) I've even feed them table scrapes chicken, steak(chew it a little first) pork
, raw bacon cooked even (my tsn loves this), hot dog's ( only once in awhile prone to rasie nitrate level and a greasey sheen my appear on the surfus of the water)good pellet food as well(I mix hikari cichlid gold with cichlid staple they love it )flakes if you wish (omega one is my choice african cichlid brand high seafood content) and of course time but mostly water changes are key in the control of this and lateral line errosion common in oscar's to ..... some my disagree but this work's for me ! best of luck to you.. 
