BRS just had a video on the Hanna phosphate and phosphorus checkers. Their testing which included a standard regent showed that using the phosphate checker a measurement did not record until the level of phosphate reached .08. The phosphorus checker tested exactly as the standard regant of .02. They saw no point in going lower. This surprised me because my phosphate checker was always showing .00. So in frustration I bought the phosphorus checker and my test whit it showed .0397 I would think the company would show in their literature.