The Milwaukee CD97 is a digital pen-style meter designed to provide fast and accurate measurements of Total Dissolved Solids (TDS) in your water. It is an essential tool for saltwater aquarists to verify the purity of their source water from filtration systems like RO/DI units, ensuring a clean foundation for mixing new saltwater. By monitoring the parts per million (PPM) of dissolved solids, you can easily determine when your filters need replacement and maintain optimal water quality for a thriving reef environment.

This TDS pen features a low measurement range from 0 to 999 ppm, which is ideal for checking RO/DI water, and includes automatic temperature compensation (ATC) for consistent readings. It boasts a resolution of 1 ppm and an accuracy of ±10 ppm. The unit comes factory calibrated for immediate use but also allows for simple, one-point manual recalibration if needed. With an impressive 300 hours of continuous use from the four included 1.5V batteries, this meter is a reliable and long-lasting instrument for your aquarium maintenance routine.

This cost-effective and easy-to-use tool is perfect for any reef hobbyist who relies on an RO/DI system. It gives you the confidence that you are starting with pure, 0 TDS water before adding expensive salt mix, preventing the introduction of unwanted contaminants like phosphates and silicates. Its simple operation and clear display make it suitable for both beginners learning about water chemistry and experienced aquarists performing routine checks to ensure their filtration equipment is performing at its peak.