If the fish in the pond have been gasping at the surface for a few days, read this article before it is too late. I will give you some tips to avoid having fish gasp and die.
A possible cause may be excess ammonia in the water.
A large quantity of tree leaves deposited at the bottom of the pond, during the process of transformation into slime, generates ammonia in the water, which is poisonous to fish.
The problem arises especially if you walk in the pond. In fact, when everything is still, practically nothing happens. If, on the other hand, you walk on it, a large amount of ammonia is suddenly released.
The same phenomenon can happen if you put a pump that draws water from the bottom of the pond that it is full of slime and leaves. You should never draw water from the bottom, otherwise all the water become dirty and you facilitate the release of ammonia again.
You have to act preventively: do not let too many tree leaves settle at the bottom, and never scrape the bottom: silt is natural and must be present in all ponds!
If you really find yourself in the extreme situation where after many years you have a 20 to 30 cm layer of leaves at the bottom, and you have to remove them, quickly do a partial water change to dilute the excess ammonia released in the water.
Another cause of excess ammonia in the water is the presence of too many fish in a small space.
Fish foul the water a lot because of their excrement and because of the excess feed given to the fish.
The larger the size and number of fish, the greater the risk of excess ammonia.
The smaller the volume of water in the pond, the greater the risk of excess ammonia.
A high pH facilitates the conversion of ammonium (produced by fish excrement and rotten leaves) into ammonia, thus endangering fish health.
To avoid this risk, keep an eye on water parameters such as pH by periodically doing this test.
The pH in a pond should be between 6.5 and 8, i.e. neutral to slightly alkaline. If the pH is above 8, use a pH reducer such as sodium bisulphate to normalise the water parameters and thus also to keep ammonia formation under control.
To summarise, if the fish gasp and die, or only gasp (for the time being):
- change the water partially to reduce the concentration of dissolved ammonia in the water;
- test the water parameters and check that the parameters are within the normal range. If the pH is too high, reduce the pH and monitor the water parameters over time.
Another possible cause of fish gasping is lack of oxygen (this is common in a pond with few aquatic plants).
In conclusion, fish gasp and die due to lack of oxygen in a pond without aquatic plants or with newly planted plants.
In a pond with already well-grown aquatic plants and in the right amount in proportion to the surface, the cause of fish gasping is usually due to excess ammonia.
By the way, if you have a pond and want to avoid problems of dirty water, overpopulation of fish, and thus excess ammonia in the water, instead of big fish such as koi carp or goldfish, put in small medaka, which do not create these problems.
You can find more detailed information on how to choose suitable plants and obtain a balanced pond in this free Video Course!