The nitrogen cycle starts when a source of ammonia is placed in the tank. Over the course of about a month, the ammonia concentration will rise, triggering the nitrifying bacteria to multiply. The ammonia concentration will reach a peak level and begin to drop when the bacteria have multiplied to sufficient numbers.

This is a very dangerous time for any fish in your tank. There is no way to determine how concentrated the ammonia levels will be before the peak is reached. As a general rule, the more fish you have in your tank, the more concentrated the ammonia level will become before the peak is reached. If you have fish in your tank at this time, it is probable that they will die, and there is nothing more discouraging than removing dead fish from a new tank.

As the ammonia levels begin to drop, the nitrite concentration will rise. Eventually it will also peak and begin to drop. The nitrites will reach much higher levels and maintain those levels for a much longer period of time: The bulk of the cycle is consumed by the nitrite peak. It is important to remember not to perform water changes until the ammonia and nitrite levels have dropped to zero during the cycle period, or the cycle will take longer. Test the ammonia and nitrite levels at least once a week for the next three months and watch for the ammonia and nitrite levels drop to zero.

Some advocate purchasing a single fish to start the nitrogen cycle, but we do not promote this form of torture here at Willa’s Ark. An alternate method that has gained popularity throughout the fish keeping community is fish-less cycling. Drops of ammonia are placed in your fish tank to kick start the nitrogen cycle, and in some cases, complete the cycle sooner. And the best part: No suffering or dead fish! To see how the fish-less cycling works, click here.