Zeolite is a natural remedy for the removal of ammonia.
When placed into your pond it will readily absorb ammonia from the water.
After a period of time the zeolite will become saturated with amonia and can be refreshed.
Remove it from the pond and the ammonia dispersed by placing it in a bucket of strong saline solution.
(It should be rinsed before being returned to the pond).
There are no hard and fast rules about the use of zeolite because each pond has differing amounts of amonia and fish.
It should be remembered that ammonia can kill your fish so you should test your pond regularly using a test kit.
Tip: Zeolite should always be soaked in a saline solution (1 Kg salt to 10 litres water) before use.
This will remove any ammonia absobed from the atmosphere and also to recharge.