Welcome to Simply. Unfortunately, you'll need to unlearn reef techniques to successful raise discus. Here's an example.
My tanks have a heater, a sponge filter and fish.
All the money is focused on getting superior genetics.
At our local fish shows, I spend a lot of time looking at the reef tanks. The reefers also spend a lot of time looking at my discus. Here is the fundamental difference between two very different tank set ups.
A reef tank is an exercise in restraint. Huge amounts of equipment is used, most of which is trying to take out nutrients and metabolites. The system is extremely delicate so a lot of technology and very little biomass are requirements for success. Raising discus, in contrast, is like raising pigs. Dump a lot of food in the trough, hose it out, rinse and repeat. Do it consistently and you'll get great fish. Do it inconsistently and you'll get stunted footballs.
Good luck, Willie