Published November 30, 2012
If you know anything about maintaining a healthy, thriving saltwater tank you probably know the basics of the nitrogen cycle. The nitrogen cycle is the process through which beneficial bacteria in the tank work to break down ammonia, a by-product of decomposition of waste products, into less harmful substances like nitrite and nitrate. All three of these substances are toxic to fish in high doses which is why it is important for you, as an aquarium hobbyist, to understand how to control them. In order to keep your fish safe from the dangers of high ammonia, nitrite and nitrate you need to understand where these substances come from, what effects they can have on your fish and what you can do to prevent high levels of these substances in your tank.
Causes of High Chemical Levels
Beneficial bacteria require nutrients in order to thrive and to maintain the nitrogen cycle – those nutrients are derived from the organic waste products that accumulate in the substrate of your aquarium. Some of the organic wastes likely to accumulate in a saltwater tank include uneaten fish food
and fish feces along with the occasional dead fish. The more waste that builds up in your tank, the harder your colony of beneficial bacteria will have to work to maintain the nitrogen cycle. The by-products of the nitrogen cycle are ammonia, nitrite and nitrate so it makes sense that, the harder the beneficial bacteria in your tank are working, more of these substances will be produced. In short, the ammonia, nitrite and nitrate levels in your tank are directly related to the amount of organic waste that is allowed to build up in your tank substrate. If you keep your tank fairly clean, performing routine water changes and siphoning the substrate on a regular basis, you are less likely to have problems with high levels of ammonia, nitrite and nitrate in your tank.
If the ammonia, nitrite or nitrate level in your tank is allowed to get out of control, it could have serious consequences for your fish. Prolonged exposure to either high ammonia or nitrite levels can lead to poisoning and even death in saltwater aquarium fish. Ammonia is extremely toxic and it can irritate and damage the sensitive tissue in the gills of your fish – with prolonged exposure, your fish may suffer permanent gill damage which could affect their respiration as well as their ability to expel excess ammonia from the body. Nitrite poisoning is closely related to ammonia poisoning because high levels of one often accompany high levels of the other. Brown blood disease is a nickname given to nitrite poisoning because this condition often results in an increase in met hemoglobin in the blood of aquarium fish which gives it a dark brown coloration. An increase in met hemoglobin may significantly reduce the ability of blood cells to carry oxygen which could result in suffocation, even if there is oxygen available in the tank water.
Nitrates are less harmful to aquarium fish than nitrite but, in high doses or with prolonged exposure, they can still be dangerous. Nitrate is the third by-product of the nitrogen cycle and the ideal level in a healthy aquarium is below 30 ppm (parts per million). When nitrate levels reach 100 ppm or more it could cause fish to become extremely stressed which will result in an increased susceptibility to disease
– it could also inhibit the reproductive capabilities of your fish. In newly-hatched fry and juvenile fish, high nitrate levels may also lead to stunted growth or abnormal development.
The most effective way to control the ammonia, nitrite and nitrate levels in your tank is to control the amount of organic waste you allow to accumulate in your substrate. Try not to overfeed your fish
and avoid overstocking your tank – the more fish you have in your tank, the more waste that will be produced. It is also important to perform weekly water changes of 10% to 20% your tank volume – water changes are the only way to completely remove nitrates from your tank. If you don’t perform routine water changes, the nitrates in your tank will become more and more concentrated to the point where it becomes a toxic environment for your fish. If you perform these simple tasks and precautions, however, you should have no trouble maintaining healthy levels of ammonia, nitrite and nitrate in your saltwater tank.
Howe, Jeffrey C. “Aquarium Nitrate Trouble.” FishChannel.com. < http://www.fishchannel.com/fish-magazines/freshwater-and-marine-aquarium/august-2009/aquarium-nitrate-trouble.aspx>
Wittig, Shelli. “Water Changes.” Cichlid-Forum.com. < http://www.cichlid-forum.com/articles/water_changes.php>
Helm, Ben. “Controlling Ammonia in a Fish Aquarium.” FishChannel.com. <http://www.fishchannel.com/fish-health/healthy-aquariums/controlling-ammonia.aspx>
“Nitrites in the Aquarium.” Algone.com. < http://www.algone.com/articles/aquarium-filtration/nitrites-in-the-aquarium>