The Nitrogen Cycle of a Saltwater Aquarium

The nitrogen, or nitrifying cycle in saltwater aquariums, is the basic biological cycle that is a continuous process in established tanks. Put simply, it is the balance of certain chemical elements resulting from the natural environment.

To start the cycle, you must have ammonia. This is combination of the chemicals nitrogen and hydrogen. Ammonia comes from the urine and excrement of fish, as well as leftover food and decomposing plants and fish. That means you will need to add fish to your saltwater aquarium, even though the nitrogen cycle has not started, which can be hard on the fish. Most hobbyists will start off with just a few fish, to minimize any losses, and also to build the ammonia level slowly. After 7-10 days, the nitrifying bacteria should appear, and start to break the ammonia down into the next part of the cycle, which is to turn it into nitrite.

Again, while nitrite levels are building, it can endanger fish because of the elevated levels needed to establish the cycle. It can take anywhere from 25-30 days for the levels of nitrite to even out, and start producing nitrobacters, a bacteria that feeds on oxygen and food, and excretes nitrates into the water, which begins the cycle all over.

Because saltwater aquariums have different requirements for fish only tanks and those with natural coral reefs, it is important to test the various components of the cycle at regular intervals, so that you know just where your levels of ammonia, nitrite and nitrates are, relative to what is needed for a healthy environment.

Recommended: You'll find more information on starting your own saltwater aquarium, we recommend picking up the Complete Encyclopedia of the Saltwater Aquarium.

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