Salinity advice needed

[Dub]

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?

 

[Cory]

Id make one of Randys reference solutions

http://reefkeeping.com/issues/2004-06/rhf/index.php

 

[anthonygf]

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?

I would go with the refractometer only. If you can afford it go with the digital refractometer, I have a Milwaukee brand been using for almost 2 years and keeping mine at 1.025 with no problems. Very easy to use and I check mine daily, sometimes more when I do a water change.

 

[Cory]

I disagree the milwaulkee isnt good for reefkeeping. It isnt accurate enough. Its accuracy is 2% iirc. So 1.026 could be 1.028 or 1.024. I have one and was disappointed.

That said it seems all your devices read similar if you account for temperature of sg.

 

[anthonygf]

I disagree the milwaulkee isnt good for reefkeeping. It isnt accurate enough. Its accuracy is 2% iirc. So 1.026 could be 1.028 or 1.024. I have one and was disappointed.

That said it seems all your devices read similar if you account for temperature of sg.

Mine seems to be accurate compared with outside water testers and my optical tester. Been using it for close to 2 years. Maybe you had a bad device?

 

[BrandonS]

Are you floating the calibration fluid in your tank for your refractometer before calibration. That way it's same temp as tank

 

[anthonygf]

Mine seems to be accurate compared with outside water testers and my optical tester. Been using it for close to 2 years. Maybe you had a bad device?

I also use a Hanna pocket tester and get the same readings.

 

[Randy Holmes-Farley Verified Community Expert]

The calibration fluids posted above should help determine what is most accurate, especially if you have a scale to measure them.

At the end of the day, salinity is not very critical and the differences between these devices are not enough to cause a substantial issue.