The Nitrogen Cycle

Before you buy your first fish, you need to grow your first bacteria. This process is called "Cycling" your tank.

In the ocean, waste is diluted by billions of gallons of water. In your glass box, fish waste (ammonia) builds up instantly and can become toxic. The Nitrogen Cycle is nature's way of processing this waste into something safe.

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The Three Stages

Step 1: The Source (Ammonia)

When you set up a new tank, it is sterile. There is no bacteria. To start the cycle, you need to introduce Ammonia. This is usually done by "Ghost Feeding" (dropping fish food into an empty tank) or adding pure liquid ammonia.

Never cycle a tank with live fish. It causes unnecessary suffering and permanent gill damage to the animal.

Step 2: The First Colonizers (Nitrosomonas)

As Ammonia builds up, specific bacteria called Nitrosomonas begin to populate your rock and sand. They consume the Ammonia and excrete Nitrite.

During this phase, if you test your water, you will see high Ammonia levels dropping and Nitrite levels rising.

Step 3: The Second Wave (Nitrobacter)

Once Nitrite is present, a second type of bacteria called Nitrobacter arrives. These bacteria consume the Nitrite and convert it into Nitrate.

This is the longest part of the wait. You will see Nitrite spike off the charts, and then suddenly drop to zero overnight.

Step 4: The Finish Line

Your tank is "Cycled" when you can add Ammonia (food) and, 24 hours later, test your water to find 0 Ammonia and 0 Nitrite, but some reading of Nitrate.

At this point, perform a large water change (50%) to lower the accumulated Nitrates, and you are safe to add your first fish!