If you have a pond, particularly one that contains fish, you must deal with the amount of ammonia that builds up over time, as fish continuously excrete ammonia as part of their metabolism. Ammonia also builds up from wastes and decaying food and is often found naturally occurring in water too. Ammonia can cause sickness and be fatal to fish and other living organisms, so it must be controlled. It's best to keep your ammonia levels at zero for the health of the pond.
Use an ammonia test kit to find the amount of ammonia in your pond. Purchase test kits at any home improvement store. Take a water sample and add the enclosed drops. Wait 15 minutes and compare the water with the colour on the chart.
Install a bio-converter to your pond. Proper filtration will keep your ammonia levels where they should be.
Apply an ammonia chemical treatment into your pond water if you prefer to not add filtration. As a general guideline, apply 50 millilitres to every 100 gallons, but different ammonia treatments may call for differing dosages. Test your water again 24 hours after the first application. Reapply if necessary until the level reaches zero.
Reduce the amount of food by half if you are feeding fish. Build-up of food can increase the ammonia levels.
Remove all fish and place them in other water if the ammonia level is more than 2.5 parts per million. Return the fish once the ammonia level is back to zero.