Water changes depend on why you are changing water. If you use the EI fertilizing method, you need water changes to keep from building up too much of each fertilizer in the water. If you use ADA aquasoil you need water changes for a few weeks to keep the amount of ammonia in the water down. If you keep messy heavy eating fish you need water changes to keep good water quality. Etc.
I use the EI fertilizing method, but I dose daily instead of 3 times a week. I also use a continuous water change system that adds about 10 gallons, for now, of replacement water to the tank every day, a few drops at a time. (45 gallon tank.) I do that for convenience, to maintain a constant water level in the tank, and to avoid big buildups of any of the fertilizers.
I use the EI fertilizing method, but I dose daily instead of 3 times a week. I also use a continuous water change system that adds about 10 gallons, for now, of replacement water to the tank every day, a few drops at a time. (45 gallon tank.) I do that for convenience, to maintain a constant water level in the tank, and to avoid big buildups of any of the fertilizers.