it doesnt matter that pygos are more hardy than discus, i like pristine water in my tanks, i like to do things differently, if everyone did a water change every three days im positive there fish would be thriveing more than they are now, thats a fact, i just really really care about my fish, frontosas rhoms pygos w/e they are all treated the same, like sensitive discus, many hobbyists would like to do my routine but they feel bad because they cannot so they try and find excuses why you shouldnt do that many water changes, like i said im sure once a week is super, good luck with your fish