Fungal Aquarium Fish Diseases

Icthyophonus

• Diagnosing systemic fungal infections, including Icthyophonus, is rare and difficult. Freshwater and marine tanks kept cool at 38 to 68 degrees Fahrenheit, with decomposing plant matter, deceased fish and excessive build-up of organic waste creates the greatest risk of icthyophonus. (See Reference 1) Infected fish often exhibit a curved spine and a sandpaper-like texture on their body. Icthyophonus spreads by cannibalism of infected fish and through the release of fungal spores in feces. (See Reference 2) Doctors Foster and Smith recommend malachite green immersion baths to cure the fungal disease. (See Reference 1)

Egg Fungus

• Achyla and saprolegnia fungi attack eggs during fish breeding. The white, fluffy fungi target damaged, infertile and diseased eggs first. Then, by close contact, the fungi can spread to healthy eggs. Parent fish usually eliminate eggs with problems, leaving behind only healthy eggs. Egg fungus infections commonly exist in fresh and brackish aquariums where the egg-laying fish has died and the eggs are left unprotected. (See Reference 1&2)

  Saprolegnia fungi can attack both eggs and fish. Fluffy pieces of white, gray or brown material attach to the fins, gills or eyes of fish in tanks with high ammonia levels and poor water circulation. (See Reference 2)

  Prevent achyla and saprolegnia, also known as cotton wool disease, by avoiding over-populating the aquarium, using a fully-functioning filtration system and by removing organic waste from the tank with routine cleanings. (See Reference 1 &2) Treat these fungi with gentian violet, formalin, potassium permanganate or povidone iodine solutions. (See Reference 2)

Gill Rot

• Branchiomyces, or gill rot, commonly affects aquariums with algae blooms, low oxygen levels or low pH levels hovering around 5.8 to 6.5.(See Reference 2) High levels of nitrates and ammonia can also cause this fungus. (See Reference 1) Fish infected with gill rot gasp for air at the top of the tank. The gills may appear patchy, with areas of dying tissue or a mucus-like substance. (See Reference 2 &1) As infected gills fall off, fungal spores released into the water make healthy fish in the aquarium susceptible to infection. Formalin and copper sulfate will treat gill rot, according to The University of Florida's Institute of Food and Agricultural Sciences. (See Reference 2) Increasing oxygen levels in the aquarium and long-term therapy of phenoxyethanol baths also reduce branchiomyces. (See Reference 1)