This handy pen-style tester gives you precise TDS and pH readings in seconds — just dip it in your tank water and read the result on the clear LCD display. With a measurement range up to 9990 ppm for TDS and 0–14 for pH, it covers everything from freshwater tanks to reef setups. Compact enough to store in a drawer, it's an essential tool for any aquarium keeper who wants to stay on top of water quality. Available as a TDS-only, pH-only, or combination unit.