Refractometer

[backwoodssteve]

After year of using this I decided I should calibrate it I use distilled water it was far off then my friend told me I should calibrated every time before I use it it continually gives me a different reading I can test my water calibrated it test my water again and get a different reading they used to use one of the plastic ones that you fill with water it works on specific gravity not as accurate but consistent I have a glass tube that's for specific gravity of heavy liquids I floated out in the salt water does not give me the same reading as the refractometer what can I do to get accurate readings

 

[Randy Holmes-Farley Verified Community Expert]

What brand refractometer?

Many are not true seawater refractometers and should be calibrated with a 35 ppt seawater standard and NOT RO/DI (regardless of manufacturer claims) because they are meant for sodium chloride brines and not seawater.

Also, is it an ATC (automatic temperature compensation) refractometer? If not, the temp can be important.

For your floating glass hydrometer (which is what I'm guessing you mean by a glass tube), temperature is ALWAYS critical, and it will only give accurate values at a single temperature. Does it say what temp it is calibrated for?

 

[backwoodssteve]

Magnum media rhs-10atc. I looked it up on google it appears to be a cheap one it wasn't at the reef shop though my hydrometer is calibrated for 60 degrees Fahrenheit its getting frustrating main tank has had ups and downs lately and I wasn't sure why but now I think I know

 

[Randy Holmes-Farley Verified Community Expert]

The refractometer won't be too far off with DI water calibration, but best to use a standard. You can make your own or buy one, but Di water will suffice till then.

The floating glass hydrometer should give a very different reading due to its calibration temp. Don't bother with it for now.

 

[jlanger]

I just figured out that my calibration fluid was off by 0.005.
Since I calibrate my two refractometers with the same fluid, my tanks were both at 1.031.
I had been complaining about poor polyp extension and overall unhappiness with my corals, and now I know why.
Needless to say, a new bottle of calibration fluid was purchased and I'm bringing my salinity back down.

Is there a shelf life for calibration fluid?
My bottle was easily over two years old.

 

[twilliard]

I just figured out that my calibration fluid was off by 0.005.
Since I calibrate my two refractometers with the same fluid, my tanks were both at 1.031.
I had been complaining about poor polyp extension and overall unhappiness with my corals, and now I know why.
Needless to say, a new bottle of calibration fluid was purchased and I'm bringing my salinity back down.

Is there a shelf life for calibration fluid?
My bottle was easily over two years old.

Interesting statement.
@Randy Holmes-Farley what is the link for the diy calibration fluid?

 

[TomatoSauceTy]

Aqua Craft makes a refractometer calibration fluid, it comes with the BRS/ATC? refractometer.

 

[backwoodssteve]

Thanks for the info and taking the time to respond.

 

[Randy Holmes-Farley Verified Community Expert]

Interesting statement.
@Randy Holmes-Farley what is the link for the diy calibration fluid?

Here's a link to the DIY:

http://reefkeeping.com/issues/2004-06/rhf/index.htm

By far the best bet is if you have a scale, but volume still works/

It never goes bad except by evaporation.

 

[Randy Holmes-Farley Verified Community Expert]

There are also now lots of commercial ones, and BRS sells several.

 

[twilliard]

Thank you Randy !

 

[Randy Holmes-Farley Verified Community Expert]

You're welcome.

Happy Reefing.