by: Brett Fogle
"Ammonia is introduced by the fish waste and decomposing organic debris, is the most toxic nitrogen compound. It is present in two forms in the pond - free and ionized. Free ammonia is the most toxic and will cause death in very low concentrations. Problems associated with non-lethal elevated levels of ammonia include gill disease, dropsy and finrot. The higher the pH and the temperature, and the lower the salinity or hardness, the greater the ratio of free ammonia to the ionized form. Thus, the higher the pH and or the temperature, the more toxic the ammonia. Test kits measure the total ammonia (free plus ionized). With a properly functioning biological filter, the ammonia level is usually zero in the pond and should be under.1ppm (mg/l). Nitrosomonas bacteria in the filter oxidize ammonia into nitrite, our next compound. If the level of ammonia is elevated, you should immediately add ammonia remover such as Tetra Aquasafe, Kordon AmQuel or make partial water changes. You should also add nitrifying bacteria to your filter and stop feeding your fish until the situation is corrected. "