On the contrary.....I am assuming you're using a nitrate test to determine water quality....Nitrate tests are affected by many other ions in the water and are very inaccurate. What is one's 10 ppm nitrate could be another's 50 ppm in the same water conditions....So one tank is not going to get water changed and the other is going to be water changed...Guess which one's tank is going to have healthier fish?....In case you're still guessing I'll simply it....Large regular water changes take the guessing out of the equation. And your fish's long term health is your indicator if you've done enough...
