Today is the hottest and most humid day we have had since I have set up my tanks 6 months ago. I do weekly water changes. Checked the salinity of my tanks and they are very low compared to normal! I usually keep them around 1.023 but today my biocube is 1.020 and my nano is 1.018! Does heat and humanity play a part in salinity? And what are some ways to compensate for this?
Low salinity question
- Thread starter Jay1661
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How are you measuring salinity ?
Was it calibrated before use ?
Was it calibrated before use ?
Yeah I do a 15% water change once a week with pre mixed saltwater at a salinity of 1.023 and top off with RO water every other day to maintain a salinity of 1.023
Except today. My water level was 2-3x lower than normal which made me check the salinity. I was expecting it to be around 1.026 but instead it was 1.020. Which was the first time I’ve ever experience this.
People are telling me temperature has nothing to do with salinity. But why is it suggested that refractometers are to be calibrated at 68F? The salinity readings I took today the water temperature was at 82F.
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Randy Holmes-Farley
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Salinity does not change with temperature. There's no uncertainty about that.
But refractive index (what a refractometer actually measures) does. If you use refractive index to try to estimate salinity (or specific gravity), then you need to either use a device that automatically corrects for temperature changes (called an ATC refractometer, Automatic Temperature Compensation), or you need to be very careful with calibrating and measuring at the same temperature.
FWIW, ATC refractoemters have a range that they claim to compensate over. If you stray outside that range, they may not do a good job, and some folks aren't especially impressed with the job they do even within the stated range (I've not evaluated that aspect myself). You can evaluate that yourself by testing water and in rooms at different temps.
I realize that some manufacturers request it, but with an ATC refractometer, it makes no sense to require calibration at a particular temperature.
Randy Holmes-Farley
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If you are interested in the details of how refractometers work, temperature effects, calibration, etc, I discuss them in detail here:
Refractometers And Salinity Measurement
http://www.reefedition.com/refractometers-salinity-measurement/
Refractometers And Salinity Measurement
http://www.reefedition.com/refractometers-salinity-measurement/
