ACES/American Crocodile Education Sanctuary recently purchased an ATC natural sea water refractometer and it isn't scaled for measurements below 20ppt. My mistake at trying to be accurate and not thinking about determining brackish and fresh water nesting areas. Dumb mistake. And I really wish I had it now to compare pre and post rainy season. I can order it and have it shipped to your house if someone could bring it for ACES.