Hello All. In my "main tank" (in profile with the Odessa Barbs and Cories) I have some solid readings [Have not updated yet but as of testing on 6/30/14 it was PH of 7.5 (Split the difference on the high and regular PH API tests!), Ammonia of 0, nitrites solid at zero, temp of 78 F but nitrates are persistently high like 40 ppm.. I even got the angry red of the 60s and 80s one time! Even with water changes it stays down there eve The fish do not show any signs of stressing or the like. Could this be from my tap water? I have two other tanks and nitrates tend to be in 30 ppms. I'm worried because this tank is heavily planted and I hoped the plants would help in lowering the nitrate levels. Any suggestions are appreciated!