Anyone use this one before?
[ame=http://www.amazon.com/Salinity-Refractometer-Aquarium-Seawater-Scale/dp/B005ES6MOQ/ref=sr_1_1?s=pet-supplies&ie=UTF8&qid=1367446766&sr=1-1&keywords=refractometer+salinity]Amazon.com: Salinity Refractometer, Aquarium & Seawater - Dual Scale (1.0 to 1.070 S.G.): Pet Supplies[/ame]
[ame=http://www.amazon.com/Salinity-Refractometer-Aquarium-Seawater-Scale/dp/B005ES6MOQ/ref=sr_1_1?s=pet-supplies&ie=UTF8&qid=1367446766&sr=1-1&keywords=refractometer+salinity]Amazon.com: Salinity Refractometer, Aquarium & Seawater - Dual Scale (1.0 to 1.070 S.G.): Pet Supplies[/ame]