im not saying its the way to go but i have a friend who keeps just 1 discus in a 130l planted community with a red tail shark, angels, fire eel, barbs etc and it is doing fine. he bought it when it was about 3-4 cm an since it has grown well. im pretty sure it thinks its another angel :roll: .
i personally wouldnt try this combo but just an example of what can be done. best thing u can do is read up as much as u can in books and on the net before u start buying discus as theyre not cheap and it sucks when they die.