As a fry, it is hard to determine the sex of the discus fish. So this is mostly a hit and miss affair. 3 inches would be the best size to buy them. But, the odds are that in those six to eight young discus fish, you will be able to get at least a pair or two. The best thing about this option is that at this age, the discus fish doesn t command a high price yet. When you are putting tap water in your aquarium, make sure that the water is treated first before you place the discus fish inside. This is to ensure that the water is free from chemicals, such as chlorine and other heavy metals. Discus fish lives naturally in soft water that is slightly acidic. When it comes to feeding, make sure that you don t over feed them. However, before you actually consider breeding your discus fish, you need to remember that breeding them can be a challenge. When it comes to breeding discus fish, there are several things that you need to keep in mind in order for you to successfully breed discus fish in your aquarium. Also, it is very important to be familiar with the behavior of the discus fish especially when they are mating or starting to breed. Any more acidic or alkaline than these numbers is a sure way to kill your discus fish. Lastly, the water hardness should also be considered. Although discus fish are not that sensitive to water hardness, it will play an important role in keeping them healthy. The optimum hardness of water for discus fish to thrive in should be between 1dH and 8dH. Setting up A Discus Fish Tank: Helpful Tips to Raise Your Discus Fish As an aquarist, you probably know that discus fish are one of the most sought after species of fish today. They are colorful and they are also fun to watch inside the aquarium. However, the problem with discus fish is that they are very hard to maintain. They thrive in streams and lakes surrounding the Amazon River. They also come from the cichid family of fish and they like deep water. For this reason alone, you may want to get the largest and deepest aquarium that your home and budget can allow. You also have to remember that discus fish are social creatures.