Okay, please do not tell anyone not to use ANY chemicals in their aquarium unless you know the condition of their tap water. Some places (such as my home town) add so mych ammonia to the tap that it kills fish almost immediatly, even after only a 10-20% water change, same goes for chlorine. so unless you are using 100% RO warter, I would add prime water conditioner (black bottle with red label), or a product called genisis (clear bottle with yellow chem). Also copper sulfate is very imporant in case your fish get ick. Dr wellfish stress coat is also good in case your fish get banged up, helps replace their slime coat, sea salt should be added to all aquriums, as it aid in the fishes respiration, and makes them more comfortable.
Never heard of it gunking up fishes gills, but if you use it "everyday" as you said, it probably is over kill.
Key to proper amonia, nitrite and nitrate lvels is not overfeeding, not overstocking, and vacuuming often, 10-20% every other week, or week depending on conditions, test often.
stay away from ph buffers, and chems that remove cloudiness, the "clouds" are the bbacteria that consume ammonia and nitrates, than produce nitrites. live plants will help reduce nitrites. messin with the ph is relativly un needed as P's are pretty adaptive to PH, and it is a pain in the ass.
Quinn