{"product_id":"saltwater-refractometer-hard-case-atc-salinity-tester","title":"Saltwater Refractometer with Hard Case | ATC Salinity \u0026 Specific Gravity Tester","description":"\u003cp\u003eGet accurate salinity readings every time with this \u003cstrong\u003epremium saltwater refractometer kit\u003c\/strong\u003e. Designed for marine and reef aquariums, it measures both \u003cstrong\u003esalinity (0–100 ppt)\u003c\/strong\u003e and \u003cstrong\u003especific gravity (1.000–1.070)\u003c\/strong\u003e on dual scales, with \u003cstrong\u003eAutomatic Temperature Compensation (ATC)\u003c\/strong\u003e so readings stay reliable even as room temperature shifts. The included hard storage case keeps everything organized and protected on your maintenance shelf.\u003c\/p\u003e\n\n\u003cp\u003ePair with \u003ca href=\"https:\/\/squeakysaquatics.com\/products\/brightwell-aquatics-calibration-standard-60ml\" target=\"_blank\"\u003eBrightwell Calibration Standard\u003c\/a\u003e for periodic accuracy checks, or browse our full lineup of \u003ca href=\"https:\/\/squeakysaquatics.com\/collections\/water-testing\" target=\"_blank\"\u003ewater testing kits and instruments\u003c\/a\u003e.\u003c\/p\u003e\n\n\u003ch3\u003eWhat's in the Case\u003c\/h3\u003e\n\u003cul\u003e\n  \u003cli\u003eSaltwater refractometer with daylight prism\u003c\/li\u003e\n  \u003cli\u003eHard plastic carrying case with foam lining\u003c\/li\u003e\n  \u003cli\u003eCalibration screwdriver\u003c\/li\u003e\n  \u003cli\u003e2 plastic pipettes\/droppers for sample transfer\u003c\/li\u003e\n  \u003cli\u003eMicrofiber cleaning cloth\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eWhy a Refractometer?\u003c\/h3\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eFar more accurate than a swing-arm hydrometer\u003c\/strong\u003e — hydrometers are notoriously inaccurate at the salinity range reef tanks actually live in.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eATC compensates for temperature swings\u003c\/strong\u003e — no need to mentally adjust readings if your sample is warm or cold.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eReads in seconds\u003c\/strong\u003e — a few drops on the prism, look through the eyepiece, done.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eDual scale\u003c\/strong\u003e — whether you think in ppt (35 ppt is reef target) or specific gravity (1.025 SG is reef target), the meniscus shows you both.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eOne-time calibration is all you need\u003c\/strong\u003e — recalibrate every few months with RODI water (sets zero) or 35 ppt reference solution for higher accuracy.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eHow to Use\u003c\/h3\u003e\n\u003col\u003e\n  \u003cli\u003eOpen the prism cover. Place 2–3 drops of tank water on the prism using a pipette.\u003c\/li\u003e\n  \u003cli\u003eClose the cover gently — sample should spread across the entire prism.\u003c\/li\u003e\n  \u003cli\u003eHold up to a light source (bright window or lamp) and look through the eyepiece.\u003c\/li\u003e\n  \u003cli\u003eRead the value where the boundary between the blue and white sections crosses the scale.\u003c\/li\u003e\n  \u003cli\u003eAfter use, rinse the prism with RODI water and dry with the cleaning cloth.\u003c\/li\u003e\n\u003c\/ol\u003e\n\n\u003ch3\u003eCalibration\u003c\/h3\u003e\n\u003cp\u003eCalibrate before first use and every few months thereafter:\u003c\/p\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eZero calibration:\u003c\/strong\u003e place a few drops of \u003cstrong\u003epure RODI water\u003c\/strong\u003e on the prism. Look through the eyepiece — the boundary should read 0 ppt \/ 1.000 SG. If not, use the included screwdriver to adjust the calibration screw under the rubber cap until it reads exactly zero.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003e35 ppt reference solution\u003c\/strong\u003e (sold separately) gives even better accuracy at the reef-tank target range.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eSpecifications\u003c\/h3\u003e\n\u003ctable style=\"border-collapse: collapse; width: 100%;\"\u003e\n  \u003ctbody\u003e\n    \u003ctr\u003e\n\u003ctd style=\"border: 1px solid #ddd; padding: 8px;\"\u003e\u003cstrong\u003eSalinity Range\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd style=\"border: 1px solid #ddd; padding: 8px;\"\u003e0–100 ppt\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003ctd style=\"border: 1px solid #ddd; padding: 8px;\"\u003e\u003cstrong\u003eSpecific Gravity Range\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd style=\"border: 1px solid #ddd; padding: 8px;\"\u003e1.000–1.070\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003ctd style=\"border: 1px solid #ddd; padding: 8px;\"\u003e\u003cstrong\u003eResolution\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd style=\"border: 1px solid #ddd; padding: 8px;\"\u003e1 ppt \/ 0.001 SG\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003ctd style=\"border: 1px solid #ddd; padding: 8px;\"\u003e\u003cstrong\u003eTemperature Compensation\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd style=\"border: 1px solid #ddd; padding: 8px;\"\u003eAutomatic (ATC)\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003ctd style=\"border: 1px solid #ddd; padding: 8px;\"\u003e\u003cstrong\u003eBody\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd style=\"border: 1px solid #ddd; padding: 8px;\"\u003eAluminum with rubber-cushioned grip\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003ctd style=\"border: 1px solid #ddd; padding: 8px;\"\u003e\u003cstrong\u003eCase\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd style=\"border: 1px solid #ddd; padding: 8px;\"\u003eHard plastic, foam-lined\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003ctd style=\"border: 1px solid #ddd; padding: 8px;\"\u003e\u003cstrong\u003eBest For\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd style=\"border: 1px solid #ddd; padding: 8px;\"\u003eMarine, reef, and brackish aquariums\u003c\/td\u003e\n\u003c\/tr\u003e\n  \u003c\/tbody\u003e\n\u003c\/table\u003e\n\n\u003ch3\u003eRecommended Pairings\u003c\/h3\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003ca href=\"https:\/\/squeakysaquatics.com\/products\/brightwell-aquatics-calibration-standard-60ml\" target=\"_blank\"\u003eBrightwell Aquatics Refractometer Calibration Standard (60 ml)\u003c\/a\u003e — 35 ppt reference fluid for periodic accuracy checks.\u003c\/li\u003e\n  \u003cli\u003e\n\u003ca href=\"https:\/\/squeakysaquatics.com\/products\/hanna-instruments-hi96822-digital-refractometer-seawater-analysis\" target=\"_blank\"\u003eHanna Instruments HI96822 Digital Refractometer\u003c\/a\u003e — if you'd rather upgrade to a digital readout.\u003c\/li\u003e\n  \u003cli\u003e\n\u003ca href=\"https:\/\/squeakysaquatics.com\/collections\/salt-mixes\" target=\"_blank\"\u003eBrowse all salt mixes\u003c\/a\u003e — consistent salinity starts with a quality salt.\u003c\/li\u003e\n  \u003cli\u003e\n\u003ca href=\"https:\/\/squeakysaquatics.com\/collections\/water-testing\" target=\"_blank\"\u003eAll water testing kits and instruments\u003c\/a\u003e — complete your reef testing toolkit.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eFAQ\u003c\/h3\u003e\n\u003cp\u003e\u003cstrong\u003eWhat's the reef-tank target salinity?\u003c\/strong\u003e\u003cbr\u003e\nMost reefkeepers aim for \u003cstrong\u003e35 ppt \/ 1.025–1.026 specific gravity\u003c\/strong\u003e. Fish-only marine tanks tolerate 30–33 ppt; reef tanks with corals do best at 35.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eHow is this different from a hydrometer?\u003c\/strong\u003e\u003cbr\u003e\nA refractometer measures how light bends through your sample — far more accurate than a floating swing-arm hydrometer, especially in the narrow 1.024–1.027 range that matters for reef tanks. ATC also compensates for temperature, which hydrometers don't.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eDoes it come with calibration fluid?\u003c\/strong\u003e\u003cbr\u003e\nThe kit includes the refractometer, hard case, droppers, screwdriver, and cleaning cloth. For zero calibration, use your own RODI water. For best accuracy at reef salinity, pair with a 35 ppt reference solution like \u003ca href=\"https:\/\/squeakysaquatics.com\/products\/brightwell-aquatics-calibration-standard-60ml\" target=\"_blank\"\u003eBrightwell's calibration standard\u003c\/a\u003e (sold separately).\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eHow often should I calibrate?\u003c\/strong\u003e\u003cbr\u003e\nCheck calibration with RODI water every 1–2 months. If you drop or knock the unit, calibrate before the next reading.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eWill it work for freshwater or pond use?\u003c\/strong\u003e\u003cbr\u003e\nThis is a saltwater-specific refractometer. For freshwater, you'd use an electrical-conductivity TDS meter instead.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eWhat temperature range does the ATC work in?\u003c\/strong\u003e\u003cbr\u003e\nAccurate compensation in the 50–86°F (10–30°C) range. Wait a moment after applying the sample for the prism to equalize.\u003c\/p\u003e","brand":"Squeaky's Aquatics","offers":[{"title":"Default Title","offer_id":48377977110747,"sku":"50001","price":29.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0767\/5209\/3403\/files\/image_ead49b45-4139-421f-9ed3-da4a0ecf0268.png?v=1773681118","url":"https:\/\/squeakysaquatics.com\/products\/saltwater-refractometer-hard-case-atc-salinity-tester","provider":"Squeaky's Aquatics","version":"1.0","type":"link"}