It removes chlorine,chloramine and ammonia, converts ammonia into a safe non toxic form and will be removed by the tanks biofilter, it can be used in the tanks cycling to alleviate ammonia/nitrite toxicity, also detoxifies nitrite and nitrate allowing the biofilter to more efficiently remove them, it can be used as slime coat too
hope this helps a bit, I onlt type out what was on the side of the bottle