Which salinity reading?

[Nemoreef]

Setting up auto water changer and mixed the bin. I wanted my salinity to be accurate so measured with

Hanna at 32.8ppm[aiming 35ppm]
BRS refractometer at 35
TM Hydrometer at 1.0275[35ppt equivalent is at 1.026?]

All measured at same temperature around 68°F and same time. Which one to trust? I calibrated hanna and refractometer right before testing. Refractometer says ATC on it so I am assuming it is temperature corrected? What am I doing wrong here?

I also saw one post from 2018 by Randy, it was actually a question to what salinity will a 35PPT at 20C change when checked at 30C. If this is the case, what salinity are we supposed to mix the bin to, if it's going to change when it reaches tank temp?

 

[CKW]

1.026 is reef aquarium standard

I don’t understand all the panic over salinity.
I suspect that when we started using refractometers they were used incorrectly. Lots of reasons for this. 1.026 @ 77 degrees f. Has been the standard fora very long time and easy to test with a simple swing arm tester.

 

[Nemoreef]

I don’t understand all the panic over salinity.
I suspect that when we started using refractometers they were used incorrectly. Lots of reasons for this. 1.026 @ 77 degrees f. Has been the standard fora very long time and easy to test with a simple swing arm tester.

How do you make sure that the testing water temp is at 77f?

 

[vetteguy53081]

I don’t understand all the panic over salinity.
I suspect that when we started using refractometers they were used incorrectly. Lots of reasons for this. 1.026 @ 77 degrees f. Has been the standard fora very long time and easy to test with a simple swing arm tester.

While I wholly agree, some reefers desire scales or target points for logging or mixing water at same salinity always. I go by ranges (1.025-1.026)

 

[exnisstech]

How do you make sure that the testing water temp is at 77f?

Heat it to 77. I have a heater calibrated to 77 just to use in fresh salt water mix.

 

[Nemoreef]

Heat it to 77. I have a heater calibrated to 77 just to use in fresh salt water mix.

yes that is an option. In this case, since it is for AWC, I do not have a heater inside the mixing bin and it is set to change only 1 gallon a day. So I didn't want to heat the water to avoid evaporation while it is waiting to be used. So I am trying to match the salinity between tank and mixing bin which are at two different temperatures. And I found out that there are conversion charts you can use which is posted in this thread.