Aquariums – health

Information about disease prevention and signs of illness in aquarium fish.

Signs of illness

Signs of illness include skin lesions such as spots, ulcers or growths, floating, listing and swimming upside down. Any form of abnormal behaviour may also indicate that fish are unwell.

Some common symptoms displayed by fish that can be easily remedied include:

  • A fish displaying signs of rubbing scales on rocks or other furniture may have parasites. These are usually visible upon closer inspection.
  • Fish appear to be gasping for breath. This is a sign of lack of oxygen in the water or very poor water quality. It suggests that the water is not being sufficiently aerated or is poor quality.
  • Puffy or swollen gills are also a sign that the water quality is insufficient.
  • Clamped fins usually suggest that the water pH is not correct.
  • Fish that do not eat for a period of 2 days or more may be stressed. This can be caused by changes to their environment including water quality, new fish being added to the tank or fish in the tank not being compatible with one another. Assess any changes that may have occurred to make the fish stressed and act upon this.
  • Red streaking and torn fins results from ammonia poisoning. This happens when water is not sufficiently conditioned.

Fish are very fragile creatures and so any abnormal sign should be noted and acted upon. If fish are showing any signs of illness or abnormal behaviour, closely monitor the fish, take note of the other fish behaviour, test water quality, temperature and pH. Fish with spots or lesions on their skin should be separated into a quarantine tank for treatment and to prevent other fish contracting the illness. Consult a fish expert, veterinarium or aquarium shop if you are concerned about the health of fish. Veterinariums and pet stores can usually supply an appropriate treatment for your fish.


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