The Hanna HI98129 Low Range pH Conductivity TDS Combo Pen is an essential, all-in-one device designed for precise monitoring of critical water parameters in saltwater reef aquariums and RODI systems. This lightweight and portable pen accurately measures pH, electrical conductivity (EC), total dissolved solids (TDS), and temperature, providing highly reliable readings right out of the box thanks to professional pre-calibration. Its automatic temperature compensation (ATC) ensures that all values are accurate regardless of water temperature.

Key features of this Hanna combo pen include its super accurate measurements, a large LCD display for easy reading, and a design that floats for convenience. It is waterproof and includes an automatic shut-off function to conserve battery life. A significant advantage is its replaceable pH electrode, meaning you only need to replace the pH cartridge when it exhausts, extending the life of the entire meter and offering a cost-effective solution compared to buying a new device.

This product is ideal for any saltwater aquarist who requires accurate, multi-parameter testing in a single, convenient device. Its ability to measure pH in the display tank and assess the purity of RODI water through EC and TDS readings makes it invaluable for maintaining optimal reef health and water quality. The durable design and replaceable probe make it a smart, long-term investment for precise aquarium management.