What Should The Ammonia Level Be in My Koi Pond? 

The best goal is to keep ammonia levels very low, aiming for 0.00 ppm (parts per million). If ammonia rises to 0.25 ppm, it signals a problem. This means the water quality is getting worse either from over feeding or stocking levels. At this level, the health of your fish is at real risk because of ammonia exposure. The gills of the fish might not work properly, making it hard for them to get rid of the ammonia building up inside them. This build up can lead to the death of the fish. with regular water tests you will be able to keep an eye on the Ammonia level as well as other levels we would recommend using NT Labs Pond Multi Test Kit.