Calibrating with distilled water?

louti · Mar 5, 2020

So, I took my water to my LFS today and they read my salinity at 1.028. I am reading 1.026 after calibrating with brightwell calibration solution. The owner said he does not trust calibration solution and only calibrates his with distilled water. I had some distilled water at home, and when I calibrated with it, I get the same 1.028 reading.

What are your thoughts? The only reason I’m questioning it is I got the calibration solution with a used tank. But it says it’s good until October of 2021.

35ppt · Mar 5, 2020

Use calibration solution, the store owner is a goof imo.

NeonRabbit221B · Mar 5, 2020

You need to calibrate around the value you are testing for.

W1ngz · Mar 5, 2020

Scientific instruments are more accurate when calibrated in the target measurement range.

If you got the solution used, throw it away and get something fresh so you know precisely how it was handled and know it was immediately closed after use to prevent evaporation.

FactoryKTMmotocross46 · Mar 5, 2020

If you are worried about it, send out an icp test and/or get a second refractometer to compare.

W1ngz · Mar 5, 2020

FactoryKTMmotocross46 said:
send out an icp test

Do they run salinity on those tests? I didn't think they did, but I've yet to get one done.

Sailingeric · Mar 5, 2020

My refractometer I got from BRS says to use only calibration fluid as distilled water will give it an incorrect reading.

FactoryKTMmotocross46 · Mar 5, 2020

W1ngz said:
Do they run salinity on those tests? I didn't think they did, but I've yet to get one done.

Ati does. I would take a reading from your refractometer after you get fresh calibration fluid the same time you fill your tubes to send for icp.

louti · Mar 5, 2020

35ppt said:
Use calibration solution, the store owner is a goof imo.

You may be right lol.

nkyreef · Mar 5, 2020

I purchased the calibration solution from BRS for my refractometer. I trust that result over using RODI.

louti · Mar 5, 2020

Thanks for all the replies. Confirmed what I have always believed to be true. I think I will pick up some new calibration solution just to be sure. For now, I’m going to trust what I have over distilled.

35ppt · Mar 5, 2020

louti said:
You may be right lol.

IME too many store owners become full of themselves and think they know it all, that they know better. Even when they're dead wrong. People think "Oh I've been doing this for 20 years I know it all" when in reality they stopped learning long ago.

Uncle99 · Mar 5, 2020

Never really bothered about whether it was 1.025 or 1.028, it’s the consistency in replicating that same number that brings the best results. So my 1.026 maybe up or down a bit, but how do you really know?
Who calibrates the calibration solution after packaging, does the salinity not slowly increase over time?
Being out a couple of points all the time will cause no grief.

35ppt · Mar 5, 2020

Uncle99 said:
Never really bothered about whether it was 1.025 or 1.028, it’s the consistency in replicating that same number that brings the best results. So my 1.026 maybe up or down a bit, but how do you really know?

Very true and likely why the store owner doesn't know the error of his ways. Stability is king, even if some parameters are not quite "correct" as long as it's stable the coral will do fine.

eggplantparrot · Mar 5, 2020

the only problem with calibrating with a calibrating solution is that you dont know for sure if its actually what is stated. i read a post or two about calibration fluids being off from the manufacturer.

i imagine the consistency of RODI being salt free is a good baseline, and if you can make your own calibration fluid with known amount of salt then it would be the ultimate calibration lol

W1ngz · Mar 5, 2020

eggplantparrot said:
the only problem with calibrating with a calibrating solution is that you dont know for sure if its actually what is stated.

I've never understood why people like that argument so much when it comes to calibration fluid, but not other products. Do you question the contents of everything else you buy? Is your salt really reef salt? Maybe they forgot to blend the magnesium that day. Is your alk buffer really pharmaceutical grade, or just baking soda? You don't know for sure if anything you buy is what's marked on the packaging.

Why is so much suspicion reserved for calibration standards?

louti · Mar 5, 2020

Uncle99 said:
Never really bothered about whether it was 1.025 or 1.028, it’s the consistency in replicating that same number that brings the best results. So my 1.026 maybe up or down a bit, but how do you really know?
Who calibrates the calibration solution after packaging, does the salinity not slowly increase over time?
Being out a couple of points all the time will cause no grief.

And I’m supposed to listen to you just because your tank looks amazing??

I agree completely. I’ve always felt that stability is the main thing.

eggplantparrot · Mar 5, 2020

W1ngz said:
I've never understood why people like that argument so much when it comes to calibration fluid, but not other products. Do you question the contents of everything else you buy? Is your salt really reef salt? Maybe they forgot to blend the magnesium that day. Is your alk buffer really pharmaceutical grade, or just baking soda?

Why is so much suspicion reserved for calibration standards?

its not an argument, just stating something that should be considered.

as the calibration fluid is something we use to measure against, it ideally has to be correct. my alk mix can be wrong, but i have something to measure that against.

again, im not arguing, just stating something that should be factored in when people talk about this stuff.

btw i use a bottle of brightwells fluid but dont trust that it is exactly 1.026, just that if i take care of it then itll be consistent at least.

NeonRabbit221B · Mar 5, 2020

Again the bigger issue is that if you plan to test in the 1.024-1.027 range then the calibration needs to be done within that range. If the calibration solution is off a bit, it is still 10x more accurate then doing a calibration outside of the standard testing range. Aim for stability and precision.

SDK · Mar 5, 2020

Calibration solution is made by measuring pure sodium chloride with a gram scale into a set amount of purified water. Done correctly it's as accurate as anything needs to be at a hobby level.

You can make your own if you are so inclined. I buy mine from BRS, and once per year throw a new bottle in my shopping cart when I'm ordering something else. It has been consistent for me from bottle to bottle.....