I bought a refractometer

[fijiwigi]

Ok I ordered a refractometer from DR Fosters&Smith. It is really nice and shiny. However I have never used one and the directions seem to make sense about how to calibrate one but I thought it may be better to hear it from a fellow aquarist in normal english. Any input on how to get started using a refractometer would be greatly appreciated.

 

[ccCapt]

Very simple to use. Put 2-3 drops of water on the lense, close the lid and look thru it. You turn the handle to focus it when looking inside.
You can calibrate with RO/DI water, but really all that does is let you set it to zero. You need to get calibration fluid. I use Pinpoint calibration fluid which is 35ppt and set my refractometer to read 35 with the fluid.

 

[austinsdad]

...or just use distilled water and set it to zero to calibrate.

 

[ccCapt]

...or just use distilled water and set it to zero to calibrate.

Well, all that does it tell you that 0ppt is correct. The hobby grade refracto's we use are not very precise. Get yourself a bottle of Pinpoint Salinity Calibration fliud. It's well worth the $4 it costs and it is a known reference solution that will let you set your refracto at 35ppt. I don't think it's just coincidence that their reference solution is set the same as NSW salinity.

 

[fijiwigi]

Well, all that does it tell you that 0ppt is correct. The hobby grade refracto's we use are not very precise. Get yourself a bottle of Pinpoint Salinity Calibration fliud. It's well worth the $4 it costs and it is a known reference solution that will let you set your refracto at 35ppt. I don't think it's just coincidence that their reference solution is set the same as NSW salinity.

could you explain why you would want to calibrate to 35 ppt and not calibrate to zero. Most things calibrate to zero how is the refractometer different exactly?????????

 

[austinsdad]

What is oppt? And whay is the solution needed if there is no SW in distilled and that sets it at zero?

But my most important curiosity would be to wonder how far off the distilled water calibration could be from the solution calibration.

Things that make you go "hmmmmmm...."

 

[ccCapt]

0 ppt means no salt in the water, at least in the case of our SW refractos. A refractometer measures how light bends when passed thru saltwater. If you do not calibrate it at a known reference point, all you know is when there is no salt in the water, the light doesn't bend and you see 0 ppt. You really have no idea if the refracto is calibrated properly when there is sw on the lense and the light bends.
FWIW, I can calibrate at 0 ppt, but when I use calibration fluid it only shows about 34 ppt so may refracto is about 1 ppt off at that range. When I calibrate at 35 ppt and use RO water, it's slightly over 0 ppt.

 

[roka64]

Just curious, is maybe the RO the cause of the difference, since you are not using the DI part?

 

[austinsdad]

Thanks. Sounds like those considering hyposalinity treatments may want to be aware.

 

[melosu58]

Well anyway good move getting the refractometer Fijiwigi