Ok, so I have been testing my nitrites daily and the odd time checking on the nitrates. Today when I did the nitrite test is was initially purple, but after five minutes turned to the pale blue for 0ppm. My nitrates today seemed lower as well, which is pretty strange, no? I shook the hell out of the bottles and did the nitrite test twice with the same result. Does it usually turn purple as soon as the drops touch the water?