Try to keep the water clean and also its chemistry stable. You have to at least change 50 percent of the water once a week and you have to make sure that the PH level is also stable. For Discus Fish, the ideal water temperature is between 82 and 86 degrees F and the hardness should be between 3 and 15dH. There are still quite a few things that you have to do to ensure that they will live a long time and save you the anxiety of having to buy new fish every time. The big news is, most fishes, including the discus fish, maybe even more so, develop health conditions because of stress. Although fishes are fragile as compared to other household pets, they don t really just die and wither if they are kept well. If the fish is passive and doesn t take interest of the new food available, this may be a sign of unhealthy fish. The fish you buy should eat the food or at least take interest in them. If the keeper says that they just fed the fish, then you should look for another place to buy a Discus Fish. As much as possible, you should buy an adult Discus Fish. They are very sensitive to water quality and also to the type of food they eat. If you don t know how to keep a Discus Fish, then you have to first educate yourself how in order for you to continue enjoying having this fish in your aquarium for many years to come. Of course, like with other pets, you want your Discus Fish to be healthy and free from disease. Make sure that you keep the pH level of the water at 6 and also the temperature at a constant 82 to 86 degrees F. If you want to add other species of fish in the discus fish aquarium, make sure that you try adding catfish, plecs, small tetras, and other gently and slow moving fish from South America. And, the best thing about these fish species is that they go along with discus fish and can really enhance the look of your discus fish aquarium. You have to remember that discus fish are schooling fish that likes to be kept in small groups of five to eight. They need security of a school around them and getting them in groups will help in reducing their stress levels and also help in keeping them happy.