I read that the maximum percent of water change you can do is 50% ? Is there a reason why you can't change 70% of the water? Can someone explain to me why you can't.
I've seen this done with discuss (and fry) a lot...huge water changes. But the fact that you mentioned he was selling them is the reason for the seemingly drastic water changes. By changing the water everyday he is eliminating growth stunting hormones which all fish release. Basically, he was making his discuss grow faster so he could sell them for more money. You wouldn't need to do 80% water changes everyday if you ever got discuss. Don't be discouraged, lol.I once came across a person selling Discus cichlids. He had a 125 gallon tank, filtered by Eheim 2262 and a 30 gallon refugium. He told me he did 80% WC EVERYDAY !!
He can get away with it as he had the refugium, so he stated.
Anyways, that ended my curiosity about keeping Discus cichlids.....geez I want a life !!