Odd fish death

[Brent F]

I have heard of this soon after a water change. One guy I knew when I lived in Edmonton had a tank maintenance service and had something similar happen after doing water changes in a couple tanks. He was using tap water with chlorine remover. The chemicals in used in the tap water were different one week and he had fish die in a number of tanks. The water tested fine.

This wouldn't be the problem if you are using RO water.