There are three stages in the nitrogen cycle. The process takes time — anywhere from two weeks to two months or more — so you have to be patient.
Stage one of the nitrogen cycle is the introduction of ammonia. Ammonia can come from uneaten fish food, tropical fish waste, and other sources. Waste and food can break down into ionized ammonium (NH4) or un-ionized ammonia (NH3). Ammonia is what can be harmful or deadly to your fish. The water’s pH level will determine what the food and waste break down into — ammonium or ammonia. If your pH is less than seven, you’ll end up with ammonium. If the pH is more than seven, you’ll end up with ammonia.
Stage two of the nitrogen cycle is when the bacteria start to work. Bacteria called nitrosomonas will start to oxidize the ammonia, creating a byproduct called nitrites. Nitrites are just as toxic to fish as ammonia is — so you’re still not ready to introduce fish into the tank. Nitrite levels generally start to rise around the end of the first or second week.
Stage three of the nitrogen cycle will introduce another kind of bacteria — nitrobacteria. These bacteria will convert the nitrites into nitrates. Nitrates are not as deadly as nitrites and ammonia, but can still cause problems in large amounts. But nitrates are much easier to deal with! You can clean nitrates out of your water through partial water changes. Simply monitor your tank’s nitrate levels and perform a partial water change when necessary. Live aquarium plants in your freshwater tank can help use up nitrates, too. Live rock and deep sand beds with anaerobic bacteria can help break down nitrates in a salt water tank.
Want to move things along more quickly? Here are some tips to help you speed up the nitrogen cycle:
- Keep the water warm — between 80 and 82 degrees Fahrenheit (between 27 and 28 degrees Celsius).
- Borrow gravel from an established and cycled aquarium to help introduce good bacteria.
- Use an extra filter from another (established and cycled) tank or a friend’s established and cycled tank to help introduce good bacteria.
- Talk to the folks at your local pet or aquarium store about products that can help introduce good bacteria.