Hach/Environmental test strips are manufactured with a unique reagent pad at the tip and use proven chemistry to test for Nitrate / Nitrite in swimming pools. Keeping nitrate levels in check helps prevent rapid algae growth.
To test for nitrate / nitrite in your pool, just dip the strip, wait until color development occurs, and compare the color of the reacted pad to the chart printed on the bottle. It's that easy! 25 test strips per bottle.