I follow the instructions of salt mix but refrac. reads different salinity ????

I follow the instructions of salt mix (crystal sea salt mix) " 1 Ib to 4 gallons = 1.023 salinity" but refrac. reads different salinity 1.019 ????

 

That ratio does not sound right!!! i do 1.5 lb per 5 gallons and it gives me 1.025

 

Make sure you have calibrated your Refractometer. Also temp. has an effect on your salinity.

 

Yes! If yours is an auto temp calibrating, make sure the sample sits for atleast 30 secs. Also, as precautionary measure, every time I take it out of the box, I check RODI water to make sure it is zero.

 

Here's where it get's tricky. You can calibrate a NSW refractometer with RO/DI water and it will be 100% accurate. The instructions for NaCl refracts also say to calibrate with RO/DI water or Distilled water and those will be inaccurate by .0015 SG by doing so.(Borrowed from Curts refractometer thread) I would use a calibration solution to make sure it is accurate at the range we need.(1.023-1.026)

 

The directions are also just an estimate I thought, not to be exact.

Mine says 1/2 cup per gallon for 1.023 I think. I keep my tank at 1/026; this am it was 1.02575ish.

After about as 1/2 cup per gallon, then I always just adjust by small amounts anyways to get it where I want.
The directions are going to make it look like you can make more SW than you really are able to usually with a given quantity of salt. IMHO

And checking the accuracy of your measuring device is always advised, as said.