Unionized ammonia exists by itself, while ionized ammonia can only exist as part of a compound, such as ammonium hydroxide or ammonium chloride.
The proportions of free ammonia and ion depend on [pH] and water temperature. When these factors increase, so does the proportion of free ammonia, which is toxic to fish. ammonium ion is non-toxic as it cannot penetrate into fish tissues.
Among the adverse effects of free ammonia we can highlight the following: + Growth inhibition + Decreased fertility + Decreased defenses against diseases + Irritation of the nervous system, with spasms and jumps as a consequence. + Loss of color on fins + Gill destruction
The tolerance of fish to adverse effects will depend on: + Type and size of fish + General health status + Oxygen shortage + Excess carbon dioxide + Electrochemical balance
It is known that 0.2 mg of free ammonia per litre lead to an increase in the respiratory rate of fish.
Carbonic anhydride reduces the toxicity of free ammonia to concentrations of 15 to 60 parts per million, although after these values the toxicity increases markedly. Before a water change that changes the pH, the ionized ammonia value should be known.
When pH is less than 7 nitrification stops, so ammonia cannot be oxidized by bacteria. For example, a concentration of ammonia of 10 parts per million has a highly lethal effect on an aquarium with a pH value of 9 (alkaline), while the same concentration will be harmless in an aquarium with a pH value of 6 (acid).
© Adrián Blanco 2005 — Prohibited the total or partial reproduction of text and/or images without explicit written consent of the author. —