Discus Care actually starts with making sure that you have clean water in the tank. The most common reason that discus fish owners fail is because they did not keep the water clean. One of the labor extensive requirements is changing about 25% of the tank water at least 2 times a week. If the water is not clean it can stress out your fish. When discus fish are stressed they do not eat well and it can weaken their system. As they become weak they are prone to diseases that can kill them.