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I just measured ammonia and nitrite using my API test kit. I waited exactly 5 minutes as instructed and recorded one reading. A came back 5 (or so) minutes later and decided to double-check my reading. This time I read a higher value. (Nitrate looked the same both times.) Note that I did not re-run the test, I simply looked at the same vial against the color chart again.
Some test kits, such as my Red Sea iodine kit, specifically say results are stable for only5 minutes and not to rely on them after that time. But the API ammonia and nitrite test kits say no such thing.
So which is the correct result? Do these tests continue to get darker with time, or do they converge on the correct reading and simply need more than 5 minutes?
Some test kits, such as my Red Sea iodine kit, specifically say results are stable for only5 minutes and not to rely on them after that time. But the API ammonia and nitrite test kits say no such thing.
So which is the correct result? Do these tests continue to get darker with time, or do they converge on the correct reading and simply need more than 5 minutes?