One product that is easily overlooked are in-line TDS monitors. While these are popular, most hobbyists purchase a lower end model. However, we’ve been hearing whispers from aquarists about a DM-2 model which is a huge upgrade from the still very popular DM-1 model. It’s designed for commercial or industrial applications with a stronger, water resistant casing. Calibration can be done simultaneously or individually on each line and reading the monitor is a breeze with an larger easy to read LCD display. A variable mounting bracket and waterproof shielded cables. The premium for this model is only about $5-10 more then the standard DM1 model. Very few marine stores carry this model, even Marine Depot doesn’t, and they are all things “marine” right? Apparently not.