Causes and diagnosis
Fish gasp for air when they cannot absorb enough oxygen through their gills. This happens if the dissolved oxygen content in the water drops below 5 mg/L or when toxic substances block absorption. Sturgeons have a higher oxygen demand and are often the first to experience problems with a deficiency.
The water temperature plays a crucial role because warm water can physically hold less oxygen. In addition, aquatic plants and algae consume oxygen in the dark, making the level lowest just before sunrise. Measure the water values directly with a test kit to determine the specific cause.
Common causes are:
- Oxygen deficiency: mass air-gasping, often in the early morning or in warm weather.
- Nitrite poisoning: blocks oxygen absorption in the blood, recognizable by rapid gill movements and lethargy.
- Ammonia spike: caused by rotting organic waste or a poorly functioning filter.
Immediate action and recovery
Immediate intervention is necessary to prevent fish mortality. Immediately increase water movement by turning on all fountains, waterfalls, and air pumps. Run this equipment 24 hours a day to continuously add oxygen and drive harmful gases out of the water. Never turn off the aeration at night, especially in warm weather or with a lot of vegetation.
Perform a partial water change to quickly add oxygen-rich and cooler water. This also dilutes any concentrations of ammonia or nitrite. In case of acute poisoning, change up to 50% of the volume, but try to avoid large temperature shocks.
Follow this recovery plan:
- Place extra air stones, waterfalls or fountains in the pond for maximum oxygen supply
- Immediately change 20 to 30% of the pond water with tap water
- Stop feeding completely until the behavior normalizes and the water values are stable
- Remove organic waste such as leaves and sludge from the bottom to stop further pollution
- Clean filter material only with a bucket of pond water to spare the bacterial culture