I live in a chronic drought area now so I do less than an optimum 50%+weekly WCs...But all my tanks are at least medium or more planted with low fish stocking. I'm a rare tester, but when I do, I never see more than 5ppm nitrate at most. I know that's not the entire tank picture as Bob alluded to, there's a major "squish factor"...but some of that comes with experience...When in any doubt, change more water more often! That's my mantra & has been for almost 30 years. It works!