This handy pH pen/meter is a great tool for any aquarist. It is extremely easy to use and is waterproof. Simply dip the meter in the solution to get the pH reading. Its high accuracy and resolution also make it suitable even for the most-demanding applications.
Note: pH 7.0 solution is required for calibration.
Captive Purity manufactures water filtration and water testing supplies for marine and reef aquaria. The brand is best known for their high-quality line of reverse osmosis filter systems and accessories. Captive Purity also produces refractometers for testing salinity, portable pen-sized meters for testing pH as well as replacement filter media for their RO and RO/DI filter systems.