Astronomical nitrate levels

[Jeff S]

I did a water change several months ago due to excessive ammonia. I put the water into a container, added a gallon jug of hydroton with an air line inserted to see if I could preserve and use the nutrient water in my outdoor gardens. Today when I measured the nitrates they were off the scale with a ppm of 1330. I kept diluting the water until finally getting the test water to change from dark red to just red...8 to 1. Of course the ppm's dropped to 210. Is there such a thing as too many nitrates for plants? Can nitrates grow on their own over time?