Big water changes, lots of them. I recommend if you don't have the time and convenience to do massive frequent water changes, to think twice about getting discus, any discuss expert will tell you that, filtration is secondary, meaning that it's all about the water change. A bare tank bottom is best to keep it clean and feeding is a challenge, they will shut down and not eat certain foods.
Temp at 84f. And I would not mix any other fish with them, though I've seen it done, can't speak for long term.
It took me a long time to learn the hard way, meaning I had some failures, till I followed the steps above, now is just second nature, but that will be the only way you'll keep healthy discus.