Tropical Fish Forums

[tripwater]

OK, I just got my refractometer in today. I calibrated it and tested my water and I am not real sure how to read this so here is what I see

on the left the line is at 1.021 SG(I assume salt gravity) and on the right it has salinity numbers.

My water temp is 83f


again not sure what I am reading in this eye piece so any helpful hints or knowledge in this regard would be great. I found in another post that the ideal levels for salinity is 1.023-1.028.

As specific as salinity is in most of the threads I have read, is this not a wide range? I have read that SW fish are pretty sensitive to the salinity levels...I guess most are referring to a sudden change in the salinity levels when discussing this...

So as long as I stay within the 1.023-1.028 range I should be fine? Do I need to add more salt?

thank you for your time

[sirreal63]

Let's go back to the beginning...what did you calibrate it with? if not calibrated correctly it can cause issues.

It is best to keep it at 1.025.
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110 Gallon DSA Pentagon

[tripwater]

distilled water. That is what the instructions called for

thanks for the reply

[Michael L.]

I read somewhere that RODI and distilled water were not good to calibrate with, regardless of what the manufacturer says. Where can you get a sample of water for calibration? Mine is currently calibrated using the RODI method, but I don't really know if I should trust it. It reads just slightly under my hydrometer, so I think it is okay now, but not good enough for when I really get into keeping corals.

Tripwater, the "SG" part is reading specific gravity, and the other is reading salt concentration (usually in PPT).
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[tripwater]

[Michael L.]

Oops, that wasn't worded very well.

The supposed "proper" way of calibrating is to use water with a known specific gravity. This means, you would get a sample of water that you know has a SG of 1.025, and compare it to the results of your test on the refractometer, adjusting the refractometer to the proper calibration.

I was just asking anyone else if they knew where to get a "control sample" for calibrating a refractomer with.
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[gm333]

Just use r/o water its not going to be far enough off to cause a problem. Plus it beats the heck out of a hydrometer which can be 3-5 points off.