The Nitrogen Cycle

The Nitrogen Cycle is the most important part of setting up your Aquarium. No fish can survive if the cycle is not correctly completed.
Understanding the Nitrogen Cycle, it's role in aquariums and how to set up and maintain the Cycle are essential to maintaining a safe and stable aquarium environment.
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What is the Nitrogen Cycle?

At its core, the nitrogen cycle is a series of chemical and biological transformations involving nitrogen compounds. In an aquarium, it’s the process that manages waste products produced by fish, uneaten food, decaying plants, and other organic matter. Without the nitrogen cycle, these wastes would quickly accumulate to toxic levels, leading to stress, illness, or death for your aquatic life.

The cycle primarily involves three key compounds:

• Ammonia (NH3): Highly toxic to fish, even in small amounts.
• Nitrite (NO2-): Less toxic than ammonia but still harmful.
• Nitrate (NO3-): Much less toxic and manageable with proper maintenance.

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Step 1: Ammonia Production

When fish excrete waste, uneaten food decays, or organic material breaks down, ammonia is released into the water. In even trace amounts, ammonia is extremely toxic to fish, attacking their gills and causing stress or death if left unchecked.

Step 2: Conversion of Ammonia to Nitrite (Nitrosomonas Bacteria)

Enter the first group of beneficial bacteria, called Nitrosomonas. These bacteria colonize surfaces in the aquarium, such as the filter media, substrate, and decorations. They feed on ammonia, converting it into nitrite. While nitrite is slightly less toxic than ammonia, it still poses a significant threat to fish health, particularly affecting their ability to carry oxygen in the blood.

Step 3: Conversion of Nitrite to Nitrate (Nitrobacter Bacteria)

A second group of bacteria, Nitrobacter, takes over at this stage. These bacteria consume nitrite and convert it into nitrate. Nitrate is far less toxic to fish and can be tolerated at low to moderate levels. However, nitrate accumulates over time and must be managed to prevent it from reaching harmful concentrations.

Managing Nitrate Levels

While nitrate is much safer than ammonia or nitrite, it isn’t entirely harmless. High nitrate levels can stress fish, inhibit growth, and encourage algae blooms. Here are common methods to control nitrate levels:

• Regular Water Changes: Removing a portion of the water and replacing it with fresh, dechlorinated water dilutes nitrate concentrations.
• Live Plants: Aquarium plants consume nitrate as a nutrient, helping to naturally reduce its levels in the water.
• Efficient Filtration: Some advanced filtration systems, such as those using denitrifying media, can help remove nitrates.
• Avoid Overfeeding: Excess food contributes to higher waste levels, leading to more nitrate production.

Cycling a New Aquarium

At Niskai Aquatics, we believe in ethical care of your pets, and thus DO NOT support fish-in cycling of fish tanks.
We advise doing a fishless cycle, which involves adding a source of ammonia anda source of bacteria to your aquarium after it is set up.

You will need:

- An aquarium, with all components required to set it up fully (see Setting up my Aquarium)
- A source of Ammonia (fish food, CycleRight, bio-Boost Foundation etc)
- A source of Beneficial Bacteria (SeaChem Stability, pre-established biomedia, bio-Boost Foundation or bio-Boost Foundation ecoSpheres)
 

• Fishless Cycling (Preferred Method):
  1. Set up your tank with a filter, heater, and substrate.
  2. Add a source of ammonia, such as the products recommended above.
  3. Test water regularly using an aquarium test kit to monitor ammonia, nitrite, and nitrate levels.
  4. Over time, you’ll see ammonia rise, then drop as nitrite levels increase. Finally, nitrite will decrease as nitrate levels rise.
  5. When ammonia and nitrite read zero and nitrate is present, the tank is cycled.
  6. If your Nitrates read above 40ppm, do a half water change before adding fish.
  7. You can now begin to introduce your fish. (See Acclimating Your Fish for more details).

Note: If using bio-Boost Foundation or bio-Boost Foundation ecoSpheres, it is not necessary to add an additional source of ammonia as these products provide alternate bacterial fuel).

Maintaining a cycled tank:

Once your tank is cycled, maintaining the nitrogen cycle becomes part of regular tank care. This includes:

• Testing Water Weekly: Use a reliable test kit to check ammonia, nitrite, and nitrate levels.
• Cleaning the Filter: Rinse filter media gently in tank water (never tap water, as chlorine can kill beneficial bacteria).
• Performing Water Changes: Replace 20-30% of the water weekly or bi-weekly, depending on your tank’s bioload.
• Avoiding Overcrowding: Too many fish produce more waste than the bacteria can handle, disrupting the cycle.

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Troubleshooting common Nitrogen Cycle issues:

• Ammonia or Nitrite Spikes: Often caused by overfeeding, adding too many fish at once, or cleaning the filter too aggressively. Address by reducing feeding, performing water changes, and ensuring adequate filtration.
• Slow Cycling: May occur if the water temperature is too low or if the filter lacks sufficient surface area for bacterial growth. Boost the process by using a bacterial starter product or seeding the tank with media from an established aquarium.
• High Nitrate Levels: Indicates insufficient water changes or overstocking. Increase the frequency of water changes and consider adding live plants.

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