i live in a tropical country with stable water chemistry, so it may sound regular water change isn't quite discordant, but what we achieve here is not maintaining the bulk of 'old' water, but conversely, maintaining high amount of 'new' water, therefore rendering the discus to the water chemistry of our tap water condition. water change up to 90 percent is practiced by experts and breeders here, in other words, the water parameters of the tank is always maintained to the like of our tap water. i'm referring to the application on young discus, not adult discus.
Discus get used to the patterns of the surroundings, and they will know that the ugly big fish with no fins is there to change their water again. I like that 'ease' derived from 'disease' Ron! Discus are tough guys and blend with their surroundings and water conditions, but ironically, they are quite susceptible to poor water quality and infections. I might be imprecise in my last message, but to rephase it, my discus do not get stressed out according to my regular water change, but they are definitely glaring at me and suspecting fishy intents. They may be stressed if startled, i.e. knocking on the tank, sudden movement in the water etc. when changing water. So it is denpendent on the crumsy finless fish managing the water change with its barbels.
I'm not exactly sure it is proper to practice this method of water change besides tropical regions with regular water chemistry, but anyone with the fish guts to reverse to maintaining new water than old? I could not dictate which method is best for young discus and its growth, but I think it all comes down to the available water chemistry and the common practice of a region.
I agree with Discusaquarium not to purchase on-line because it is just visual purchase afterall. Choose the fish yourself and at least you are the one making the good or bad pick. Of course to pick it yourself you will need some experience and understanding of discus, best is that you employ the help of an experts. My haughty guys don't accept flakes and pellets too, and I reckon that one way is to put them on fast and offer those not so delicious cuisines to them as the only choice. But I will no do that on them beacuse they are just little kids, not that they are supposed to be naughty, but it is detrimental to their growth.