In my opinion water changing is heavily overrated. Without significant water changes my fish look best. Sensitive fish mostly do much better without changes.
I haven’t changed water for weeks and now for the first time my Dicrossus filamentosus have swimming fry. I also experienced this with Heckel’s discus. This is a hard to keep species, but without any water changes they looked great and didn’t have problems at all.
I believe water changing is only good for inducing spawning in certain fishes. Otherwise it will only ruin the tank’s equilibrium and thus harm sensitive fish.