It depends on what you are doing and what you hope to accomplish.
Math tells us:
1. You can not keep a tank at proper levels long term with water changes where the new water is at sea levels.
2. You can also not remove pollution long term using water changes.
They are effective for some things, and as part of a filter strategy, in some cases but not others. Tank size also matters. Doing a 50% change on a 10g tank with nitrates at 100 is probably the easiest option. For a 1000g tank, there are better options. That is why we see such huge contrasts in peoples experiences.
When I was breeding fish, a 50-100% daily water change was sometimes necessary. If there is a problem in a tank that needs correction a large water change is great. A weekly 10% change may help people who are not keeping levels appropriately if there livestock is low need and they use replacement water at elevated sea levels.
So a complete answer to the question, like many things in this hobby is it really depends on the situation.
Math tells us:
1. You can not keep a tank at proper levels long term with water changes where the new water is at sea levels.
2. You can also not remove pollution long term using water changes.
They are effective for some things, and as part of a filter strategy, in some cases but not others. Tank size also matters. Doing a 50% change on a 10g tank with nitrates at 100 is probably the easiest option. For a 1000g tank, there are better options. That is why we see such huge contrasts in peoples experiences.
When I was breeding fish, a 50-100% daily water change was sometimes necessary. If there is a problem in a tank that needs correction a large water change is great. A weekly 10% change may help people who are not keeping levels appropriately if there livestock is low need and they use replacement water at elevated sea levels.
So a complete answer to the question, like many things in this hobby is it really depends on the situation.