Buckeye Field Supply has just announced the availability of a 3-probe inline TDS meter for reverse osmsis equipment, called the HM Digital TRM-1. While the industry has been full of TDS meters from various manufacturers, this is the only inline TDS meter to feature three different probes. Like it’s dual probe and single probe siblings, this new TRM-1 will sport the widely used John Guest fittings, is factory calibrated with a 342 ppm NaCl solution, and can be recalibrated with a mini screwdriver. Buckeye is currently fielding pre-orders at a special introductory price of $49.99 for the three probe meter, which are expected to be in stock by mid-July. Water purity is of the utmost importance for reef keeping aquarists these days, and the best way to deliver that water is to use reverse osmosis filtration. But even the best RO filters need regular maintenance and cartridge replacements, and the only way to determine when those are due is to use TDS meters, which ultimately measure how effectively the filters are removing contaminants from the incoming tap water. For the really serious aquarium keepers, the standard two probe inline TDS meters became the industry standard, as they can be plumbed into the filter tubing to measure incoming and outgoing water purity. While this has been adequate for many years, it isn’t exactly ideal, and users needing to measure the effectiveness of specific filters have often utilized multiple dual probe meters. In most cases, however, four probes is a bit excessive, making it hard to justify the extra costs for two meters. We have a feeling that the three probe meter will be welcomed into the hobby with open arms, and we are already fans of the concept based of our own experiences.