In my opinion
- The necessity for vacuuming is almost entirely dictated by the density and type of fish, water movement/flow within the tank, and the aquascaping.
- The frequency and volume of water change required is based on the quality of the water you put, the density and type of fish, and whether or not there are things in the tank to help convert the nitrates, such as live plants.
With my mbuna they need 50% water changes each week; one tank requires much more vacuuming than the other based on the amount of rock. Their fry, in a barebottom tank but one that only has sponge filters, really need it 2-3 times a week.