Zeolith is an absolute water treatment agent for fish ponds, a great help for water treatment in all ponds. Absorbs toxic ammonium (e.g. fish droppings, rotting leaves) and reduced phosphate, and thus reduces the formation of algae. Completely non-toxic and natural. Almost essential for fish ponds. The effect lasts for about three months, after which it can be removed from the pool and used as fertilizer and soil conditioner in the garden. 1 kg of Zeolith is enough for 1000 liters of water in a tank without fish. It is recommended to double the amount for tanks with fish, and even quadruple it for tanks with carp. No risk of overdose.