Fish Suddenly Dying In Aquarium. Fish is dying by nitrogen poisoning Practice shows that in the overwhelming majority of fish dying is caused not at all by some external diseases but by mistakes in the care illiteracy and carelessness of their owners. If your aquarium fish die after a water change it likely has to do with the sudden shift in water parameters.
Choosing a tank thats too small for its inhabitants will lead to trouble. I have an established 44 gallon pentagon aquarium that has been up and running for years. Just to clarify all the fish are not dying at the same time.
The characteristic behavior is that most of the fish stand at the surface of the water and swallow air from it.
I have an established 44 gallon pentagon aquarium that has been up and running for years. So first how old is the tank setup fresh or saltwater or brackish and was it proper. No other fish show signs of stress or disease. Often aquarium fish die due to the fact that the parameters of the water have changed.
