It's all about clean water. I do daily 70% WC in my 75gal with 2 times feeding a day. Number of discus in the tank? About 30-35 young adult that is 4.5"-5" There goes the 10/gal a fish rule.
Yes.. the tank is very crowded and that's the way they like it. I don't spend time testing the water. Just do my routine WC. I also don't feed FBH as much.