I am new to this so please bear with me. I am testing the salinity of my marine aquarium. I have been using a refractometer and keeping it at 1.026 sp. knowing that the reading is hard to see clearly and knowing they have to be calibrated occasionally and that the calibration fluid might go bad I decided to go to a glass tube hydrometer. I have two glass tube hydrometers. One is calibrated to 75 degrees and is 12 inches long. The other is 7.5 inchs long and calibration is unknown. Both are older units that appear to be in like new condition. The refractometer is an older “ATC” brand unit calibrated with Accubrate calibration fluid to 1.0265 sp. Glass hydrometer s were both tested with store bought distilled water. The 12 inch unit read 1.003 sp and the other one read 1.004 sp.
Upon testing the aquarium the 12 inch unit reads 1.0245 sp, the 7.5 unit reads 1.028 sp and the refractometer reads 1.027. Water temp is 80 degrees. Should I adjust the two hydrometers for the difference that they read distilled water? What would yo say my sp is? Which unit would you use for your tests?
Upon testing the aquarium the 12 inch unit reads 1.0245 sp, the 7.5 unit reads 1.028 sp and the refractometer reads 1.027. Water temp is 80 degrees. Should I adjust the two hydrometers for the difference that they read distilled water? What would yo say my sp is? Which unit would you use for your tests?