Understanding the nitrogen cycle is essential for every koi keeper. This biological process converts toxic fish waste into less harmful compounds.
The cycle in three steps:
Ammonia -- Produced by fish waste, uneaten food, and decaying organic matter. Extremely toxic. Must be zero in an established pond.Nitrite -- Beneficial bacteria (Nitrosomonas) convert ammonia to nitrite. Still very toxic. Must be zero in an established pond.Nitrate -- A second group of bacteria (Nitrobacter) converts nitrite to nitrate. Much less toxic but should be kept below 40 ppm through water changes.Cycling a new pond:
A new pond has no beneficial bacteria and will experience ammonia and nitrite spikesFull cycling typically takes 4-8 weeksAdd only a few fish initially to limit ammonia productionTest daily during cyclingUse water changes to keep ammonia and nitrite below 0.5 ppm during the cycleSigns your cycle has crashed:
Measurable ammonia or nitrite in an established pondCommon causes: over-cleaning filters (killing bacteria), power outage, medication that killed bacteria, sudden increase in fish loadTreatment: immediate water changes, reduce feeding, add aeration