Copper sulphate

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What is it?[edit]

Copper sulphate (sulfate) is a chemical used in the treatment of some bacteria, algae, fungus and some fish parasites such as Ich. It can also be used to kill snails, accidentally or on purpose.

  • This chemical is toxic if the wrong dosage is used.[1]

The disadvantage of copper sulphate is that it is extremely toxic in water of low alkalinity (KH). NEVER use copper sulphate without testing the total alkalinity of the water, carefully measuring the dimensions of the actual water volume of the tank to be treated, and weighing the amount of chemical to be applied.

The concentration of copper sulphate to apply is often calculated by determining the total alkalinity of the water and dividing that number by 100.

For example:
If the total alkalinity of the pond is 120 mg/l, then 120/100 = 1.2 mg/l of copper sulphate.


  • Do not use copper sulphate if the total alkalinity is less than 50 mg/l as it will seriously harm your animals.
  • Use of copper sulphate may lead to severe oxygen depletion, therefore, vigorous aeration should always be turned on before adding the chemical.
  • This will add levels of copper to your tank which will very likely kill any copper sensitive invertebrates as well - do not use in a Reef tank!
  • Please ensure you read and understand the links and references provided before use.


  1. Ichthyophthirius Multifiliis (White Spot) Infections in Fish by Fisheries and Aquatic Sciences Dept., Institute of Food and Agricultural Sciences, University of Florida