I am going to share with you some things I have learnt about discus. I have had my discus for a while now and I have discovered a few things. I currently have 6 4in discus at the moment.
No. 1. Buy healthy discus- it is too hard to bring sick/injured discus back to optimum health, 2. if your drinking water is anywhere from 6.0-7.5 leave it, altering ph is fiddly, annoying, and big changes in ph are bad for discus even if only 0.5, 3. No power heads- discus do not like current, their fins are like big sails, 4. 0 ammonia 0 nitrite and 25 nitrate the limit but saying that they can live happily at 35, 5. Hardness- if your water is not that hard leave it but if it is too hard use peat or drift wood, 6. large water changes- every day, every second or once a week depending on your situation but the large water changes dramaticly lower nitrate, 7. no chemicals- use conditioner for chlorine and all that doodad but dont use algae controlling products or water clearing agents (as my janitor I use a bristle nose pleco they eat the algae, uneaten food and the slimy coating that comes from the discus.
When buying discus look at them very closely!!!
-Look for small eyes in proportion to the body, if they have big eyes and a small body they are stunted.
-Round body excluding fins, some geneticly bad discus are oddly shaped from oval to square.
-High erect fins, if the fins are down they are sick or very scared.
-bold colors, pale discus are sick but keep in mind the small discus may have not developed their full colors yet.
-eager to eat, when you walk up to the tank they should swim up to you and follow you.
Do not be affraid to haggle. I bought a discus marked at $80 for $30, the discus was slightly off shape so therefore got him cheaper with a little convincing-Dont forget aquariums/breeders want to sell their discus.
Well I hope this helps. Discus really are the king of the aqarium and with a little work and patience are easy. :)