Why are my fish swimming at the surface?
Why are my fish swimming at the surface? If this is the case, a generous water change should be done immediately (80-90%). The reason is that the water quality in the aquarium is very poor. Most likely, there is an acute nitrite or ammonia poisoning, which can be fatal for the inhabitants of the tank, as they can no longer breathe properly.
In the next few days, if possible, water should be tested regularly, several small water changes should be made and no feeding should be done. In addition, you need to find the reason for the poisoning. Often the filter, overstocking of the aquarium, too much food or a dead animal is responsible.