What Are Normal Ammonia Levels?

A healthy aquarium should have no measurable ammonia. In a new aquarium, the presence of ammonia means that the tank has not been properly "cycled." In a mature aquarium, ammonia may be present if the aquarium contains too high a bioload (amount of life forms), the mechanical filtration is broken or needs cleaning, or too much filter media or substrate (gravel or sand on the bottom of the tank) has recently been replaced.

  1. Cycling

    • Cycling means allowing a tank's beneficial bacteria to build up in the substrate, on plants or rocks, and in the filter media. Beneficial bacteria create the aquarium's biological filter, which converts ammonia into less harmful nitrites and nitrates. Generally, cycling is accomplished by letting a tank run without fish for two weeks or longer, but the process can be accelerated by adding water, substrate, or filter media from a healthy, mature tank to the new tank.

    Ammonia

    • Ammonia is produced by fish waste and by uneaten, decaying food or plants. Ammonia is highly toxic to fish. A tank with the correct amount of biological and mechanical filtration for the bioload in the tank will quickly convert ammonia into less harmful nitrites and nitrates. Any pet store with an aquarium section will sell ammonia test kits.

    Nitrites

    • Ammonia is converted into nitrites by beneficial bacteria living in your aquarium's substrate and filter media. A tank with high nitrites may need more filtration, mechanical or biological. Or you may need to feed your fish less.

    Nitrates

    • In the third step of the ammonia-to-nitrate cycle, bacteria converts the nitrites into nitrates, which are less harmful than ammonia or nitrites. Nitrates are removed from the water during regular water changes. Plants and algae use nitrates as food.

    Water Changes

    • Even in a healthy tank, you should change about 15 percent of your water volume per month to remove excess nitrates and nitrites. You may change more if your tank is suffering from excess nitrates, nitrites or any amount of ammonia. You do not want to change more than 30 percent of your water volume at once, unless the tank is "crashing" (the fish are going belly-up.)

    New Tank Syndrome

    • "New tank syndrome" occurs when something containing a great deal of beneficial bacteria--the substrate of the aquarium or the sponge in a mechanical filter, for example--is removed or replaced with new materials containing no beneficial bacteria. The result is that the nitrogen cycle fails and ammonia is not properly converted into nitrates.