Agree. Even discus, which I kept for years, have no need for daily water changes with the right approach to feeding and keeping them.If doing the 10% daily water changes makes you feel good, knock yourself out. But they're not necessary.
Unless the tank is polluted with lots of excess food, a good 50% or so water change weekly is plenty.
Nematodes, for one. A healthy fish might be resistant enough to deal with them if not overloaded, but not a stressed fish. Feeding live earthworms is one of those things some people might get away with, but not something I'd do with my own fish.Exactly what parasites would aquatic fish get from terrestrial earthworms?