Bluelab pH PenOverview Plants get their nutrition from minerals but they can only get all the right minerals they need if certain conditions are right. A key factor that affects food uptake is whether the solution is acid or alkaline. This is measured in pH. The Bluelab pH Pen is the latest innovation for hand held meters. It provides a compact, quick and handy way to manage the success of crops, to ensure maximum uptake of nutrients. Teamed with the Bluelab EC Pen