Disease management in ornamental fish

Like other captive animals, aquarium fish  are vulnerable to a range of diseases, many of them triggered by stress such as  overcrowding, excessive noise, aggression from other fish, poor water quality,  or changes in temperature or water chemistry. Commonly experienced problems in  aquaria include "Ich" or White spot disease, a skin infection caused  by the protozoan parasite Ichthyophthirius  multifiliis, which manifests as small white spots over the body and  fins; ‘fin rot’, where fishes' fins turn whitish and die back, often following  damage or injury, which is caused by bacterial or fungal infection; and various  internal or external parasites.

The names commonly given to disease  problems encountered by ornamental fish hobbyists, such as ‘dropsy’, ‘pop-eye’,  ‘fin rot’ and so on, are mostly descriptions of symptoms rather than specific  diseases. They may be caused by a wide range of disease agents, most of which  are poorly understood. Although some diseases, such as White spot disease, can  cause grossly visible signs in fish, the actual cause may not be determined  without suitable training and the aid of a microscope, or other specialist  diagnostic tests. A veterinarian should therefore be consulted for disease  diagnosis, and gross signs alone should not be used to diagnose disease in  fish.

The keys to minimising disease problems  in ornamental tanks and ponds are to manage the fishes’ environment to minimise  stress, to maintain water quality, ensure there is no over-crowding, and to  always quarantine live foods and new fish before adding them to the tank.

Finally, great care must be taken in  disposing of dead fish, waste water or other materials from fish tanks, as many  diseases of ornamental fish can spread into the wild and affect native fish  populations. For example, in 2005 Murray cod  were found to be highly susceptible to a dwarf gourami iridovirus, an outbreak  of which caused 90% losses in farmed Murray cod  in Victoria.  Similarly, outdoor fish ponds should be carefully sited and built to prevent  overflows from reaching natural waterways.

Tips for ornamental fish owners

  • Dispose of dead fish and all waste from  aquarium tanks responsibly, ensuring that no water or waste enters any drain or  waterway.
  • Give unwanted fish to a friend or a  pet-shop, or dispose of humanely.
  • Design fishponds so that plants,  snails, fish or eggs can’t escape during heavy rains, and screen all overflow  areas. Consider keeping species native to your local area.
  • If you have unhealthy looking fish,  seek appropriate treatment advice from your local aquarium shop or  veterinarian.
  • Quarantine live food prior to  introducing it to your aquarium or pond, to ensure that any diseases or  parasites are not spread to your fish!

Additional information

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