PURE Aquarium balls maintain crystal clear, healthy water in aquariums of all sizes. Inside every 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 clarity. PURE aquarium canont be overdosed. 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 into the filter. If using PURE Aquairum for the first time or if your aquarium has clarity problems, add 5 to 10 balls per 100 litres of water. When the water clears use as normal. PURE Aquarium can also be used when starting up a new tank to help mature the filter. Each pot contains on average 50 balls