Bro what is your objective of this qn?
1st of all, there is no fixed amount for water change. Also water change depend on how well your bacteria can cope with your bioload.
In addition if i keep fishes that are below $50, will I take the trouble to do water change weekly? Ans is no. If good mood, 20% mthly i consider very good liao.
Before i decommed, I do 50% weekly for my 6ft fowlr cos i notice by doing that, fishes were more lively and have fast growth rate. Colours were also brighter.
Tank size matters too. For a 3ft tank, doing 50% salt doesnt cost as much as doing 50% for a bigger tank. So for smaller tank ppl dont mind changing more water n more often to a bigger tank.