Calibrating A Refractometer?

[VictorMeldrew]

Hi all

i have just tested the S.G in my tank and the result was, 1.005, this surely can not be correct, i mixed the salt at 1.025 just a few days ago when i done a water change, my fish and coral's are all doing very well and my salt level has been fairly consistent so far, so i decided to check the calibration of refractometer, i know you need distilled water to calibrate, but all i have is cold water that has been boiled in the kettle, i have taken a reading of this water and it is off the scale, well below 0, My questions are, shall i re-calibrate to the, cold previously boiled water and adjust my salt level from there? is boiled water the same as distilled water? Is it possible for any livestock to be happy at such a low salt level?

Thanks
VM

 

[The-Wolf]

if your lfs sells marines fish, ask then to calibrate it.
ideally you should use RO water not distilled and any lfs that sells marine will have RO to hand.

 

[VictorMeldrew]

if your lfs sells marines fish, ask then to calibrate it.
ideally you should use RO water not distilled and any lfs that sells marine will have RO to hand.

Thanks Wolf, RO water, i didn't think of that, i have a few drops left in my containers, problem is, i do my salt mix in them so the water is already salty. I can not get to the lfs until the weekend, shall i just wait, 1.005 must be a false reading, everything looks fine in the tank. I calibrated with the kettle water the first time, do i adjust back to that or just wait?

I will re-calibrate at a lfs at the weekend but until then what should i do?

Thanks
VM

 

[kj23502]

I would venture to speculate that if that reading were accurate you'd be having trouble w/all your inhabitants. Anyone near you have one in working order that you could check with? Friend, neighbor..someone like that? My lfs calibrated with R/O but some on here say it's better to calibrate with a known solution. Such as a known 1.025 solution. I think I'll just use R/O water for now. The other can be ordered online from sciency places. (On the other hand, if you order the solution and this issue comes up again, it would be really easy to check it. Not sure on the shelf life of the stuff, though.)




Kj

 

[andywg]

if your lfs sells marines fish, ask then to calibrate it.
ideally you should use RO water not distilled and any lfs that sells marine will have RO to hand.

Distilled water is purer than RO and as such would perform as well or better.

While what the wolf says is right for lab grade equipment, the refractometers we use are cheap and drift from 0 to 35 ppt. As such calibrating to zero does not guarantee accurate marine water measurements. A known salinity solution around 35 ppt is much better. Ski has a link ( I believe it is in the realm of knowledge) to a DIY known salnity solution.

 

[The-Wolf]

While what the wolf says is right for lab grade equipment, the refractometers we use are cheap and drift from 0 to 35 ppt. As such calibrating to zero does not guarantee accurate marine water measurements. A known salinity solution around 35 ppt is much better.

I bow to a greater knowledge than I

 

[GShorty1981]

Just use a Hydrometer Refractometers are a waste of time unless you paid alot of money.

 

[kj23502]

Just use a Hydrometer Refractometers are a waste of time unless you paid alot of money.

Hydrometers aren't all they are cut out to be. You drop it and it's basically scrap(the swing arm).

Ok ok it's 35ppt which equals a sg of 1.025 or 1.026. Now can't remember exactly which one So basically the same thing. I said just said the sg instead

 

[GShorty1981]

I use a float hydrometer and i did have a refractometer which i sold to my mate as they both gave the same results.

 

[SkiFletch]

And this is exactly why I posted things in the Realm of Knowledge