The first thing to do is to test the water – especially for ammonia and nitrite. High ammonia and nitrite cause fish to suffer
respiratory problems, and they will gasp at the water surface to try to get some oxygen. Low dissolved oxygen could also
be a problem.
You need to increase the aeration and carry out a partial water change. It is important to find out the cause of the
incident to prevent it from happening again. Check that the filter is working correctly, and that the tank is not dirty.
Make sure you maintain the tank regularly and change the water.
Oxygen is consumed by excess waste and sludge in the aquarium; so if you have a problem with low DO, make sure that it is
not caused by a build-up of dirt and sludge! Keep your tank clean by siphoning the gravel every few weeks and by removing