Water changes may have attained some religious status among discus keepers.. but even myths are based in facts if you dig deep enough...and though it may be a myth to some that frequent water changes are necessary to raise big, healthy , well developed discus....its a fact that water changes remove accumumated waste, decrease parasite numbers, allow for intensive feedings associated with good Growth and developement of Discus.. How much to change varies depending on tanks, equipment, water parameters, and hobbyists goals and experiences. My biggest problem with when people say that water changes aren't needed is that the hobbyists new to all this usually wind up paying the price when they follow that line of thinking as "advised"... Doing water changes isn't a guarantee that you'll raise great fish...but it really helps as a starting point by removing variables that more experienced Hobbyists take for granted, IMO.
So theres my 2 Cents on water changes and discus....and yes..I change water here.
hth,
al...doing water changes as I type