1. You won't be able to do any painting - even zero VOC formulas - after getting fish so now is the best time.
2. With that much surface area exposed, humidity is going to be a major problem as discus tanks run 82 - 84F. You may need a whole basement dehumidifier. These are pricey, but will go a long way to maintaining home values, and marital harmony.
3. I have GCFI receptacles in my fish room, but have regrets because some are difficult to reach. If I had a do-over, I would install GCFI circuit breakers which are much easier to reset.
4. Discus need water changes so you'll need to make provisions to do them in a 220-gallon tank. Instead, consider starting your discus in much smaller tanks, maybe a 40-Breeder, and move them into the big tank as adults.