Refractometer, make sure it's calibrated.

[reef-treasure]

i always use 2 refractometers and average their results to get a good reading.

 

[Randy Holmes-Farley Verified Community Expert]

Hi Randy. The standard I use is from Naslow Chemical Ltd. called Seawater Calibration Solution. 1.025 SG. To be honest I have no idea where I purchased this product and a google search doesn't seem to find it anywhere.

OK, I'd be wary of it. I don't see it online either, and a no-name company may not understand how to make such things.

 

[Brian Kim]

I've been using the same meter for a couple years. Never had a problem. Mix my salt the same everytime. Check my salinity about once a month. Usually it deviates between 1.025 and 1.026 somewhere. Guess its a good time to calibrate. I'm confused though by what everyone is saying? Is it okay to use DI water or should I use calibration solution. And should I calibrate at room temp, tank temp, or something else? Everyone has a different opinion but what would work best? My refractometer is from BRS. Thanks!

Calibrate at room temperature "always" made the mistake of calibrating using 50 degree water myself with readings off by 0.005
edit: my brute container holding my change water and ro/di is in my garage and when I checked the temperature it was around 49

 

[Randy Holmes-Farley Verified Community Expert]

Calibrate at room temperature "always" made the mistake of calibrating using 50 degree water myself with readings off by 0.005
edit: my brute container holding my change water and ro/di is in my garage and when I checked the temperature it was around 49

FWIW, if you want to take mesurements in the garage, just keep a 35 ppt standard there as well. Having both at the same temp should minimize any errors.

 

[redfishbluefish]

i always use 2 refractometers and average their results to get a good reading.

???? So on average, your specific gravity is off, unless both read the same exact number, that happened to be right. Reminds me of a statisticians explanation of his day at the shooting range. The first three shots were 5 inches to the left; the next three shots were 5 inches to the right; on average, he shot all bullseyes.

 

[Jlobes]

???? So on average, your specific gravity is off, unless both read the same exact number, that happened to be right. Reminds me of a statisticians explanation of his day at the shooting range. The first three shots were 5 inches to the left; the next three shots were 5 inches to the right; on average, he shot all bullseyes.

I was thinking the same thing. If your instruments are calibrated and working properly, should give you the same reading. sounds like one of these things is not like the other

 

[Brian Kim]

FWIW, if you want to take mesurements in the garage, just keep a 35 ppt standard there as well. Having both at the same temp should minimize any errors.

Yes...I finally received my 53 mS test kit (can't believe I paid 15 bucks for a small bottle of 35ppt water lol) and upon testing it in my garage it was also .005 off due to the low temperature.

 

[joeyhatch11]

Using the solution and calibrating to 35ppm on my Vertex Refrac my tanks are coming back at a 1.023. Using RO/DI and re-testing, I'm getting 1.024 on both. So not as bad as I thought. Will use the solution now that I have it and up my SG to 1.025 with the next couple water changes and see what that'll do for my tanks and SPS.

 

[Randy Holmes-Farley Verified Community Expert]

FWIW, my revised Refractometer article has just published in the December issues of ReefEdition here at Reef2Reef:

Refractometers And Salinity Measurement
http://www.reefedition.com/refractometers-salinity-measurement/