I totally disagree. Many discus keepers do daily water changes of up to 90% without any issues. In fact with discus it is often recommended to do more water changes instead of less. As long as your parameters are pretty much matched when doing these water changes, I doubt this is your problem.
Where did your discus come from? Was the tank cycled before you added them? How long has the tank been set up? Discus are pretty sensitive and with all the feeding in a small tank it would be pretty easy for the ammonia to spike IMO.
I agree that many do large scale changes. But they probably know the water make up of the fresh water they are putting in. I had the same problem several years ago that he is having now. Once I checked with my water company and found out what was in my water and changed my technique I did not have anymore problems. He need to get a test kit and find out about his water.
What do I need to find out about my water? I know it is chorinated, has a hardness of about 50, comes out at a pH of about 8.0 and after it degasses for 24 hours settles at around 6.8. Any of that help?
