ebay refractometer not reading correctly

Hi folks,

I picked up an ebay refractometer (I know, some of you might be already shaking your heads). It is listed as a salinity refractometer, and has a built in SG scale to 1.070.

Problem is, I am not getting the right readings from it. a SG of 1.020 (measured by my hydrometer) is 1.035, and an SG of 1.040 is 1.065, even after multiple calibrations with distilled water.

I was under the assumption (correct me if I'm wrong) that SG is SG, no matter if its for salinity, sugar, or whatever.

I have the option to return it, but has anyone out there had a similar experience?

You need a sugar refractometer. There is a difference (though I couldnt tell you what!).

I did a little research, and realized the error of my ways.

It should have been obvious to me, that a saline solution does not have the same refractive index as a sugar solution. so even though the meter shows S.G., it's a translated S.G. estimated on saline, not sugar. oops!

Anyone want to measure the salinity of their fishtank?

Maybe there's a conversion from saline to sugar? So you can make a chart, etc?