Hey Kerrie I’d say the more the better . For young discus for me 50% daily. As they get to a year or so you can knock it down to every other day. Now on my older tank it’s every 2 days 50%. On the new tank it every other at 50%. This will also depend on the size of your tank. The smaller the more water changes. A smaller tank is easier to grow young discus. Less water to change. Not sure what they get out of the new water but they do need it. My tanks are perfect 0/0/10 but if I don’t change the water on time 2 of my discus will get white dots on there fins. 3 water changes later there gone. Clean water is really the most important thing.