I've never bought this brand so maybe it's an accident. I always test new strips with old ones and with the API master test kit. Old test strips simply tend to show less registered presence, ie. copper or nitrates. Both my old strip and the API test kit showed nitrate levels below 25ppm, but these test strips showed no nitrate at all. And also the tests have an oddly low pH compared to the other 2. I threw them away and threw the money in the trash.
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