Pure aquarium balls maintain crystal clear healthy water in aquariums of all sizesr inside very ball there are millions of live bacteria and enzymes which start to break down ammonia and nitrate once added to your aquarium pure aquarium also breaks down organic waste which is often the cause of poor water clarityr pure aquarium canont be overdosedr to maintain crystal clear water add 1 or 2 pure balls per 25 litres of aquarium water once per week add the balls directly into the aquarium or