BLUELAB - PH PENBluelab pH Pen: The Ultimate Solution for pH and Temperature Monitoring! Plants receive their nutrients from minerals, but they can only absorb the right minerals if certain conditions are met. pH acts like a key to unlock nutrient absorption. A critical factor influencing nutrient uptake is whether your solution is acidic or alkaline, which is measured in pH. The Bluelab pH Pen also measures solution temperature, as root health is vital for a