What Causes Ammonia Poisoning in Fish?

Ammonia is a substance that's toxic to fish, though it occurs naturally in most aquariums. The problem arises when there is an inadequate quantity of beneficial bacteria to convert the ammonia -- fish waste -- into a less harmful substance called nitrate. When the ammonia level in an aquarium becomes too high, the fish could suffer and even die from ammonia poisoning. High levels of ammonia are common in new tanks that have not been properly cycled and in tanks that are overstocked.

  1. Ammonia in the Aquarium

    • Ammonia is a chemical compound known by the scientific name NH3. One way this compound may enter the aquarium is through tap water that has been treated with chloramine. The most common way ammonia builds up in the aquarium, however, is during the breakdown of organic wastes and plant matter. As the proteins from plant leaves, fish waste and uneaten fish food get broken down by beneficial bacteria in the tank, ammonia is released into the water. Although trace amounts of ammonia are relatively harmless, the ideal level for ammonia in a fish tank is zero.

    Causes of Ammonia Poisoning

    • Fish are likely to contract ammonia poisoning in tanks where the level of ammonia is too high -- fish may begin showing symptoms when the ammonia level is as low as 0.25 mg/L. The two most common causes of excess ammonia, and thus ammonia poisoning, are overstocked tanks and tanks that haven't been cycled properly. The more fish you have in your tank, the more waste will be produced. As that waste breaks down, more ammonia will be released into the water. In tanks that have not cycled properly, the colony of beneficial bacteria necessary to break down ammonia has not yet been established, which leads to a buildup of ammonia in the tank.

    Symptoms of Ammonia Poisoning

    • Ammonia poisoning tends to affect the tissues of fish, primarily the gills. Thus, some of the most common symptoms of ammonia poisoning are red streaking on the fins or body as well as red or bleeding gills. Fish suffering from ammonia poisoning could also appear lethargic, laying at the bottom of the tank; they may exhibit clamped or torn fins. Breathing difficulties and gasping for air at the surface are also symptoms of ammonia poisoning brought on by damage to the gills.

    Treatment

    • Because high levels of ammonia are usually accompanied by an increase in pH, lowering the pH in the tank should be the first step in treating ammonia poisoning. Performing small water changes using distilled water can help to reduce the pH as well as the ammonia level in the tank. Because many fish afflicted with ammonia poisoning suffer from gill damage, increasing the aeration in the tank may increase chances of survival. While chemical ammonia detoxifiers may be available, such a treatment option is not recommended because it can have long-term negative side effects.