Every new pond needs to ‘cycle’ before it’s safe for fish, and the nitrogen cycle is the process that makes that happen.
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The Three Stages
Fish waste and decay produce ammonia. One group of bacteria converts it to nitrite. A second group converts nitrite to nitrate, which is far less harmful. Both bacteria groups need to establish before a pond is genuinely stable.
How Long It Takes
Typically several weeks, not days, which is why adding fish gradually to a new pond works better than stocking it all at once.
The Trap
Testing only for ammonia and assuming the pond is safe once it reads zero is a common mistake. Nitrite often spikes right after ammonia drops, and it’s just as dangerous.
