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What is Saprolegnia?[edit]

Saprolegnia (SAP) is not an aquatic fungus, it is a Protist that is often mistaken for a fungus. It is commonly found in aquariums, particularly where there is an abundance of decaying organic matter. This can be confused with Columnaris.

Saprolegnia is spread by spores through the air and causes fungal infections in injured or sick fish or amphibians, and often attacks eggs, killing them before they can hatch.

  • This fungus spreads and eventually kills the animal.


  • Damaged skin or fins.
  • Bacteria infections which leads to further skin and fin damage.

This fungus is often seen after fin-rot or skin damage has appeared and is called cotton-wool disease due to it's fluffy white or grey appearance.


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