I water change daily only 10/15 gallons, I do it mainly to clear out his mess he makes and it only takes 5 mins instead of doing a large one once a week and taking an hour or so.5-10 gallon water changes daily with a 50% weekly seems…excessive. It’s my opinion, and what I experience with my flowerhorn so take it with a grain of salt. I do weekly water changes at between 30%-50% and have no water issues, I also test my water weekly. Again I know you may be experiencing different circumstances but daily water changes seems crazy to me. Just my two cents.