Zeolite is a mineral that have a micro-porous structure. There are used to remove certain chemicals from water.
In the aquarium hobby these small white rocks (Sodium aluminosilicate zeolite) are used to remove ammonia from the water.
Usually added to an aquarium in an emergency to quickly remove ammonia a quantity of the chips are placed in a media bag so it can be removed afterwards or simply scattered into the tank as the rock is harmless if left permanently (as long as you never add salt to the tank).
It will provide a large surface area for nitrifying bacteria.
1 gram of zeolite will remove 1.5 mg of ammonia.
The product can be recharged by the use of ordinary table salt. So no need to throw away until you have used it for many times.
To re charge take a litre of 5% solution of Salt water and soak the zeolite in it for 24 hours. Then rinse afterwards.
Working out the amount to use
Using an accurate test kit take an ammonia reading of your water in ppm (parts per million) and divide by 1.5.
Then multiply by the numbers of litres in your tank. This final volume is the number of grams of Zeolite needed.
1 tsp teaspoon of Zeolite is ~6 Grams.
The use of zeolite in a new un cycled tank is not recommended (unless in an emergency where life is threatened) as the removal of the ammonia will greatly reduce the food for the newly developing nitrifying bacteria and so will greatly increase the time it takes to cycle the tank.
Better to use a product that alters the ammonia into a harmless state that still feeds the bacteria.
Never add 'revitaliser' type products to your tank containing Zeolite. As these products are salt based and so will release the absorbed toxic ammonia back into the water.