Discus are extreamly hard to breed, i can tell you this because i am currently trying to breed discus. I kept discus for over 5 years befor i attempted to breed them. You need to be a very experienced fish keeper to breed discus. With that being said discus can have up to 200 fry in a batch. And it takes about 3 to 6 months to raise the fry to good selling size. When the fry reach about 3 to 4 inches you can sell them for about 15 to 20 us dollars. So yes there is a profit to be made but remember that you will need to buy hundreds in materials from tanks to filters and heaters to buy discus. And aquirering a breeding pair is difficult. But breeding discus is truely rewarding.