Author: Aqua Gardening

Fish Health in Aquaponics

Fish swimming in a fish tank

Unhealthy fish are often a warning that an Aquaponic system is out of balance. Symptoms such as gasping at the surface or rubbing on the sides of the tank is often because of a buildup of ammonia or nitrite. This problem in particular happens when there is too much dissolved waste for the bio filter component of the Aquaponic system to process. Below we tackle the most common causes of stress that affect Aquaponic fish health. Any of the following symptoms indicate that immediate investigation is needed - water testing - to rectify an issue.

Signs of Nitrite Poisoning in Fish


  • Difficulty Breathing;
  • Darker gills;
  • Swimming near the surface;
  • Lethargy;
  • Redness around the eyes and fins.

Remedies - use the same remedies for ammonia poisoning

Signs of excessive Hydrogen Sulphide


  • Rotten egg smell;
  • Abnormal swimming;
  • Purple / violet gills.


  • Remove organic waste which contributes to anaerobic conditions;
  • Increase aeration;
  • Increase pH;
  • Lower the water temperature;
  • Move fish to another tank until the problem is resolved.

Signs of pH Stress in Fish


  • Low pH: fish trembling or hyperactivity; difficulty breathing; increased mucus production, death.
  • High pH: opacity in skin and gills


  • Water replacement;
  • Add potassium bicarbonate to raise pH;
  • Add rainwater or pH down (phosphoric acid, not hydrochloric acid, to lower pH.

Other diseases affecting fish health

Fish health may also be affected improper salinity, too much aeration and a lack of food. With the use of potassium bicarbonate, normal aeration using an air pump and air stones, and a commercially available fish feed, these factors are unlikely to affect the health of your fish.