Fungal Infection


  • Names: Fungus, Fish Fungus
  • Disease Type: True Fungal Infections
  • Cause / Organism: Saprolegnia and Achlya mould species


Fungal infections usually start as growth on decaying matter in the aquarium. It attacks fish with a poor slime coat or eggs that have died after being laid. It will also attack lesions left by other injuries. Fish who develop fungus are already in a vulnerable state, the result of other serious health problems or attacks, such as parasites, a physical injury or a bacterial infection. Poor water conditions and drastic temperature changes can also play a part in this disease.


  • White, brown or grey cotton like growths on the scales, skin, or fins of freshwater or brackish water fish


  • Quarantine the aquarium.
  • Add aquarium salt, 1 tablespoon per 5 gallons
  • Remove Activated Carbon
  • Treat with MaracynOxy for ten days, following label instructions


MaracynOxy is the treatment of choice. It should be used according to the recommended dosage.  ParaShield is an herbal alternative, Parashield contains natural oils an extracts that have been proven effective against fungal and bacterial infections.

As with any treatment, activated carbon should be removed from the filter, as it will remove the drugs from the water.

Please note that many bacterial infections are misdiagnosed as fungal, so if unsure it is recommended to treat for both types of infection.


  • Maintain high water quality
  • Provide fish with a nutritionally balanced diet
  • Add  ParaShield whenever adding new fish to the aquarium to prevent fungal outbreaks.

Fungus is easily prevented. Avoid injuries to your fish by minimizing handling and not to mixing specimens that might damage one another. Water quality should be monitored carefully and kept high by performing regular maintenance and water changes.  The cleaner the aquarium, the less problematic fungus is likely to be.