Salinity and temp

Longnose Hawkfish · Dec 28, 2014

If I mix my saltwater at a temp of 60 degrees F will the salinty change when I bring the temp up to 75 degrees F? Thanks

Randy Holmes-Farley · Dec 28, 2014

Salinity, no. Specific gravity, a tiny amount.

BUT, depending on how you measured the salinity, or specific gravity, it might not be accurate at 60 deg F.

How are you measuring it?

Longnose Hawkfish · Dec 28, 2014

I am using a refractomer

Randy Holmes-Farley · Dec 29, 2014

Is it an ATC refractometer?

Even so, if you do not calibrate it with a 35 ppt seawater standard at 60 deg F, I would not assume it is accurate at 60 degrees.

ssdawood · Dec 29, 2014

Randy can you explain this a little more. I always get confused over this too. On my refractometer which is atc it reads 35 ppt all the time but sometimes it is 1.026 and sometimes it is 1.027.

I did buy a salinity monitor from pinpoint. How accurate are those. The monitor reads 52.4, 53, and sometimes 54 on the various standard solutions that I have purchased from pinpoint itself.

Should I always read only in ppt because that is constant and does not change with temp. To take the temperature affect out which reading will give me consistent results.

ssdawood · Dec 29, 2014

Randy Holmes-Farley said:
Is it an ATC refractometer?

Even so, if you do not calibrate it with a 35 ppt seawater standard at 60 deg F, I would not assume it is accurate at 60 degrees.

So how can one measure right salinity at all temps. Its hard to have water at 70 degrees at all times. Bucket is 65, then after heating 78. The tank itself is 78. So see the variations in temps. If lights are on temp is 80. It is all over the place.

Tell us how to measure accurate salinity at any given time of day.

Randy Holmes-Farley · Dec 29, 2014

ssdawood said:
Randy can you explain this a little more. I always get confused over this too. On my refractometer which is atc it reads 35 ppt all the time but sometimes it is 1.026 and sometimes it is 1.027.

I did buy a salinity monitor from pinpoint. How accurate are those. The monitor reads 52.4, 53, and sometimes 54 on the various standard solutions that I have purchased from pinpoint itself.

Should I always read only in ppt because that is constant and does not change with temp. To take the temperature affect out which reading will give me consistent results.

35 ppt seawater has a sg of 1.0264, but either 1.026 or 1.027 is close enough calibration.

Reading the refractometer in ppt doesn't change the concern that it may not work perfectly at temperatures other than the temp you calibrated at.

Randy Holmes-Farley · Dec 29, 2014

ssdawood said:
So how can one measure right salinity at all temps. Its hard to have water at 70 degrees at all times. Bucket is 65, then after heating 78. The tank itself is 78. So see the variations in temps. If lights are on temp is 80. It is all over the place.

Tell us how to measure accurate salinity at any given time of day.

With a refractometer, it is really the air and refractometer temp that matters since the water temp quickly comes to that temp.