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The Aquarium Cycle

Have you heard the term 'aquarium cycle' and wondered what that was? If you have just purchased your first fish tank or are new to the aquarium hobby, it is essential to understand the aquarium nitrogen cycle. Your fish will die if ammonia, nitrates, or nitrites rise too high in the tank. Fortunately, it is easy to keep these chemicals under control so that your fish stay healthy.

What is the Aquarium Cycle?

Aquarium Cycle refers to the development of beneficial bacteria in the aquarium to convert ammonia and nitrites into safer nitrates. This happens in several stages.

  • Fish produce ammonia as a waste product. Decaying plant material and uneaten food also release ammonia. Moderate levels of ammonia can make fish sick, and high levels can kill them.
  • Helpful bacteria called Nitrosomonas start to grow. These bacteria convert ammonia to nitrites. While not as toxic as ammonia, nitrites can also make fish sick, so it is important to control nitrite levels as well as ammonia.
  • As nitrites increase, another type of helpful bacteria called Nitrobacter start to grow and convert the nitrites to much less toxic nitrates.
  • Live plants and algae use nitrates to grow. These nitrates act much like fertilizer for them, and the plants draw them out of the water.

Once the different bacterial colonies have grown to sufficient numbers, ammonia, nitrites, and nitrates will be at or near zero. Sometimes the colonies can fluctuate, so it is important to test regularly for these chemicals.

Essential Items for the Nitrogen Cycle

There are some items that all aquarium owners must have to start and maintain a healthy fish tank.
Here are the most important items:

  • A biological filter large enough for your aquarium
  • Gravel or other substrate on the bottom of the tank
  • Testing kits for ammonia, nitrites, and nitrates—these can be multi-test strips or electronic meters
  • Testing kit for pH (lowering the pH can help fish survive if ammonia spikes)
  • Bucket for water changes

One or more live plants will help keep nitrate levels low. Adding beneficial bacteria to the aquarium at start-up can speed the nitrogen cycle. If ammonia rises to dangerous levels, there are products that can neutralize the chemical so that the fish are not harmed.

Important Things to Remember

During aquarium start-up, check the ammonia, nitrite, and nitrate levels daily. If the levels are high, make sure to do water changes in the needed amounts to lower the waste products and keep the fish healthy.

Don't add too many fish at first, and choose fish that have a better chance of surviving the aquarium cycle. Add two or three small fish to the tank to start, and select species that are hardier like Blue Damsels for saltwater aquariums, and Danios, White Clouds, Rasboras, Barbs, or small Cory's for freshwater aquariums. Once the ammonia and nitrite levels drop to zero after four to six weeks, you can add a couple more fish every two weeks. Avoid overfeeding your fish. This will prevent the leftover food from contributing to the ammonia level.

Do you have more questions about the aquarium cycle? Ask the friendly staff at Aquarium Supply! Call them today at 949.429.8034 or use the helpful contact form. They will walk you through the first critical weeks of the nitrogen cycle to ensure your aquarium is established successfully.

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