I heartily disagree. :wink:Razzo said:20% wc twice per week should be plenty to keep nitrates down. If not, you need to find out why and correct that problem. 50% is too much at one time! And twice per week at 50% is way too much.
There's nothing wrong with changing out 50-75% of your tank water, provided you match water parameters. Needing to change out that much to maintain NO3 at less than 10ppm is pretty normal in my experience. Particularly in this case where nitrates got too high, frequent large water changes are the only way to return to high water quality.
I applaud anyone who can keep a well stocked tank with low nitrates- keep in mind that natural lakes that are highly eutrophic (and non-point source polluted) still have NO3 below 5ppm. Most lakes that you'd swim or fish in have nitrates less than 2ppm.
So, sure- 20ppm is a reasonable goal, but 10 is better. :thumb: