Nitrite Levels in Freshwater Tanks

Nitrite levels in a freshwater aquarium have a direct impact on the health of the fish. When the water is not properly monitored, heightening nitrite levels can cause illness and death of the fish. While part of the natural nitrogen cycle, nitrites can easily rise to dangerous levels when the cycle is not balanced within the confines of the aquarium.

  1. Source

    • Nitrites are produced during the natural nitrogen cycle that happens in any freshwater fish tank. When fish produce waste materials of various sorts, they also produce ammonia. Bacteria in the water then act on the ammonia to produce nitrites, which the bacteria then oxidize into nitrates. Ammonia is present in the excrement of fish and is also released into the water during the fish's respiration process. Decaying, uneaten food that settles to the bottom of the tank also releases compounds into the nitrogen cycle. In a healthy nitrogen cycle, nitrogen-fixing bacteria convert nitrites to inactive and harmless nitrates. If the bacteria cannot adequately recycle the nitrites, the levels of nitrites in the tank can build to dangerous levels.

    How Much Is Too Much

    • Even trace amounts of nitrite are too much. A balanced aquarium should recycle nitrites as soon as they enter the system. Nitrite levels as low as .5 parts per million can have a negative impact on the fish. Nitrite levels should not be allowed to persist in the tank; permanent damage can be done to the tank's ecosystem and its inhabitants when high nitrite levels persist for more than a week. Fish will display early signs of nitrite poisoning and will warn the alert owner that something is wrong. Fish suffering from nitrite exposure will remain near the top of the tank and can appear to have difficulty breathing. These fish will not be swimming as much as usual and appear lethargic.

    Dangers

    • High nitrite levels have been linked to a number of health problems in fish, including a disease graphically named Hole in the Head. Continued high levels of nitrites not only will result in the continued erosion of the body of the fish but also will interfere with the internal processes of the fish. When nitrites are absorbed into the body, they can take the place of oxygen. The amount of oxygen delivered to the fish's vital organs decreases, resulting in the lethargy and heavy breathing seen in impacted fish. Over time, this condition will result in the decline of the fish's health and eventually death.

    Lowering Levels

    • Proper tank setup will ensure that a high percentage of nitrifying bacteria is present in the water. Start the tank with only a handful of hardy fish, such as barbs and tetras, to begin a balanced nitrogen cycle and the development of good bacteria. This bacteria will break down the nitrites and turn them into nitrates. These nitrates are harmless but still need to be removed from the tank by changing the water regularly. Add live plants, small organisms such as tube worms and a small amount of algae to also help keep nitrites under control. Change the water regularly to reduce not only the nitrate levels but the nitrite levels as well.