Why Does the Level of Nitrates Change?

Maintaining safe levels of dissolved chemicals in the aquarium is essential for keeping fish healthy and happy. Generally speaking, this is a case of correct filtering, water changing and feeding. If these factors are maintained regularly then problems with chemical buildup should be kept to a minimum.

  1. Ammonia, Nitrate and Nitrite

    • Ammonia is a compound of nitrogen and hydrogen, NH3, which occurs naturally in fish feces. Even at low concentrations in the water It is very damaging to fish, causing inflammation of the gills, which causes breathing problems. Fortunately, an increase in ammonia also promotes the growth of ammonia-digesting bacteria. These break down the ammonia into nitrites which are also harmful, but another kind of bacteria breaks nitrites down into nitrates, which are less harmful. Nitrate levels then rise in response to rising ammonia levels.

    Why do Ammonia Levels Rise?

    • Ammonia levels rise due to an increase in the amount feces in the water. This can result from too many new fish being added at once, excess of food or a break down in the filtering process. You should check all the components in your filtration system if you see a sudden spike in nitrates, it indicates that ammonia levels are rising. Also double check that you are using the right variety and amount of food for the breeds and numbers you are keeping.

    Nitrate Drop

    • If nitrate levels drop it can mean two things. One possibility is that the bacteria that break down either ammonia or nitrite have been killed off. This can happen when new medications are added to the water or there is a shock to the system such as a change in temperature or pH. Alternatively, ammonia levels could be dropping due to a decrease in feeding or better filtration.

    How much Nitrate is OK?

    • Almost any amount of ammonia or nitrite harms fish, but most species are able to tolerate some level of nitrate. Ideally nitrates should be at zero but this is almost impossible to maintain. Between five and 10 parts per million is generally acceptable. Beyond this level small water changes should be started, and if the level starts to edge towards 20ppm, then water changes of 40 percent are needed.