Originally Posted by cruiserfj45
So the best way to remove nitrate is to do a water change, but what if I have high nitrate in my tap? With my API test kit it looks like I have 10-20 ppm out of my tap. We also have hard water. Would it ok to use distilled water mixed with my tap when I do a water change? I figure if I do a 50/50 mix it will cut the nitrate's in half and keep the minerals from getting out of control.
I would calibrate the API test kit to ensure that you are truly measuring 10-20 ppm of nitrates in your tap water.
If you are on city water, there are limits to nitrates in the water supply, so you can check your local water reports to see if they agree with your measurements as an added level of certainty.
If your measurements are accurate, then your suggestion of using distilled water mixed with tap water is a good way to keep nitrates (and minerals) down.