When starting a new pond with a new filter some hobbyist prefer using ammonium chloride as an ammonia source for the nitrifying bacteria rather than load the pond with koi. Using ammonium chloride rather than koi as an ammonia source is a much safer way to seed the biofilter because the ammonia levels are not going to endanger the koi. Once the filter has cycled and the ammonia and nitrite levels are safe then you can introduce your koi. This ammonium chloride is lab grade (99.7% pure).
Available in a 500 gram jar.