ask him how he changes the water. if he is changing all of the water at once and cleaning out the tank with tap water, cleaning the filter(s) with tap water, then he could be causing his tank to cycle over and over again. that can kill the fish.
if he is taking out 50% of the water every 6 months, then that will also shock the fish. As Brian Bivens said, the tank has OTS and changing large ammounts of water in one water changes will harm the fish.
if he is taking out 50% of the water every 6 months, then that will also shock the fish. As Brian Bivens said, the tank has OTS and changing large ammounts of water in one water changes will harm the fish.
