Fish, Tanks and Ponds

Fish, Tanks and Ponds
A comprehensive guide to fish

Hypoxia in the aquarium

Silver dollar, Metynnis argenteus
Silver dollar, Metynnis argenteus


  • Lethargy.
  • Respiratory distress.
  • Gasping at the surface.
  • Fast breathing rate.
  • In extreme cases loss of equilibrium.


Hydrogen Peroxide is sold either as a 3% solution or as a 6% solution. A 3% solution is added at the rate of 2ml for every 2 gall of water and a 6% solution is added at 1ml for every 2 gall of water.

Before adding it to the tank mix the required amount of Hydrogen Peroxide with 10 times that amount of water. i.e. If you have a 20 gall aquarium and are using a 3% Hydrogen Peroxide solution you will need (2 x 20 =40) 40ml of Hydrogen Peroxide. This will need to be diluted with 400ml of water before adding it to the tank. DO NOT overdose, it is very tempting to add just a little extra to try to help them more but it will add to their stress if you do this and it won't help at all. Once in the water Hydrogen Peroxide very rapidly breaks down into water plus oxygen. Hydrogen Peroxide 2(HO) becomes H2O + O water plus extra oxygen. So there is no residue of any dangerous chemicals using this method.


This treatment will save the fish for the time being but it is essential that the cause of the oxygen shortage is rectified or the same problem will recur. Due to the nature of hypoxia rapid treatment is essential or it becomes pointless. So we recommend keeping some Hydrogen peroxide in stock.


Is a condition which occurs when a fish is suffering due to being in an oxygen deficient environment. This can occur for all kinds of reasons such as a filter failing, overdose of CO2 or even jumping out of the water and being discovered some time later on the floor just about alive. In all cases urgent help is the only way to save the fish.