Refractometer help

[EsperSol]

So I got a refractometer today, I was reading the instructions and it says to use distilled water to calibrate it. Doesn't mention anything about calibration fluid, can I use some RO water or must I go buy a bottle of distilled water?

Also sorry in advanced if this is in the wrong place

 

[ngvu1]

I wouldn't stress much over it. I would use RO/ drinking water to calibrate it for zero reading. ...I know that is not the 100% accurate but reef tanks are not a lab...minimal fluctuations should be OK. ...that is just me though.

 

[Downbeach]

You should calibrate with a solution that has a refractive index that is close to the sample you will be testing, so a 35ppt(1.026) solution would be best.

Good article here:

http://reefkeeping.com/issues/2006-12/rhf/index.php

 

[EsperSol]

Well that is two bits of very different information...So maybe I should find somewhere that sells calibration fluid

 

[CodyRVA]

Well that is two bits of very different information...So maybe I should find somewhere that sells calibration fluid

I think both approaches can be successful. If you have a reliable refractometer it's going to give you a close enough reading from calibrating with RODI. That being said, if you want a true, more accurate, measurement you should spring for the fluid. I have used both methods and noticed very little difference with my refractometer readings. Being consistent is much more important then hitting that "magic number." So, if you think you're at 1.025 and you're really only at 1.023, at least you've remained consistently on the low side.

 

[EsperSol]

I think I'm good! I just get nervous because I want things done right

 

[Pelmo]

It would be fair to use a liquid for proper calibration, but (no stress) you can use RO water without problems.
I make the calibration once a year, when I remember.
The important thing is to remain in the 1025/1026 range of density and salinity of 35-36. I prefer the 36% ° salinity.

 

[that Reef Guy]

Get Calibration Fluid.

I have tried both.

RO will be off by a Few Points!

 

[Randy Holmes-Farley Verified Community Expert]

Well that is two bits of very different information...So maybe I should find somewhere that sells calibration fluid

It's not really different info. The calibration will be off using pure fresh water (the extent to which depends on whether you are measuring ppt or sg and whether it is perfectly made or not) for calibration if it is not a true seawater refractometer (most are not unless they say so), but our tanks are very forgiving in terms of actual salinity and the expected difference in tank health is quite minor for salinity differences of a ppt or two.