Best tool to check salinity....

[Randy Holmes-Farley Verified Community Expert]

They being the manufacturer, the dd one I have is specifically for seawater they alude to the brine types in the instructions and how the one I have is accurately calibrated to zero with rodi

Then in this case, the manufacturer is partly correct. Many times the manufacturer is wrong, and a good lesson to learn early on is that a whole host of reef product manufacturers give bad advice even about their own products, which they frequently do not even understand.

It is also NEVER wrong to calibrate with a correctly made seawater standard.

 

[Jasongtr]

Then in this case, the manufacturer is partly correct. Many times the manufacturer is wrong, and a good lesson to learn early on is that a whole host of reef product manufacturers give bad advice even about their own products, which they frequently do not even understand.

It is also NEVER wrong to calibrate with a correctly made seawater standard.

Cheers, I'm sure the calibration fluid is great, but I guess if it works with rodi then that's fine, but I'll take a sample to the lfs next time I go which will be soon to determine it is actually fine of course

 

[Solo McReefer]

Bean Animal suggested Tropic Marin Hydrometer

It is very delicate

And very precise

I will be using it as the definitive calibration measurement from here on

Don't drop it

 

[Solo McReefer]

Then in this case, the manufacturer is partly correct. Many times the manufacturer is wrong, and a good lesson to learn early on is that a whole host of reef product manufacturers give bad advice even about their own products, which they frequently do not even understand.

It is also NEVER wrong to calibrate with a correctly made seawater standard.

Can you post a link to the salt you use for making the calibration fluid, please?

TYIA

 

[CO2TLEY]

Bean Animal suggested Tropic Marin Hydrometer

It is very delicate

And very precise

I will be using it as the definitive calibration measurement from here on

Don't drop it

I already dropped it lol but it was well worth getting another

 

[Reefering1]

I already dropped it lol but it was well worth getting another

 

[Randy Holmes-Farley Verified Community Expert]

Cheers, I'm sure the calibration fluid is great, but I guess if it works with rodi then that's fine, but I'll take a sample to the lfs next time I go which will be soon to determine it is actually fine of course

you seem to be taking a pretty hard line on something you are new to, and which others in this thread have been doing for decades.

Lfs is not the answer to perfect calibration.


Yes, calibration with ro/di will be perfect if (and only if) the refractometer is perfectly made and perfectly calibrated.

If it is not perfectly made, it will still correctly read 35 ppt seawater if calibrated corrrctly.

Thus, there are two reasons to use a quality standard, and there is never a scenario where a refractometer gives faulty readings using a quality 35 ppt standard.

 

[Randy Holmes-Farley Verified Community Expert]

Can you post a link to the salt you use for making the calibration fluid, please?

TYIA

Sure.

The recipe is here


Refractometers and Salinity Measurement

 

[Dom]

Who is "they'?

The they you refer to are often wrong about calibrating refractometers for some very clear reasons.

A brine refractometer (very often sold to hobbyists for marine use) is not intended for seawater and WILL NECESSARILY give incorrect values using pure fresh water to calibrate it. Calibrating with an accurate 35 ppt seawater standard eliminates the problem.

If it does not say true seawater refractometer, assume it is a brine refractometer.

I did not know this. I'm looking into a new refractometer as I am still using the first one I purchased almost 20 years ago. I'll be sure to look for one that states "true seawater".

 

[Randy Holmes-Farley Verified Community Expert]

I did not know this. I'm looking into a new refractometer as I am still using the first one I purchased almost 20 years ago. I'll be sure to look for one that states "true seawater".

Or just use a 35 ppt standard. The issues are described in great detail in the link above.

 

[Solo McReefer]

Would Morton's Sea Salt

Be a better choice to use than Morton's Iodized Salt

For the 35PPT calibration solution?

 

[Randy Holmes-Farley Verified Community Expert]

Would Morton's Sea Salt

Be a better choice to use than Morton's Iodized Salt

For the 35PPT calibration solution?

No. The recipe is designed for sodium chloride (by mass), with nothing else in it, and if you go by volume of solid instead of mass (mass is better) then even the particle size distribution matters and I'd use exactly the salt I measured out.

 

[Solo McReefer]

I would weigh it out the salt long before I would measured volume

How would one account for the air between the crystals of salt?

Even weighing the water makes more sense for me. Who is to say that a 2 L bottle from when you wrote the articles is the same size as now

35g salt to 965g water just seems easier and more precise in my kitchen to do

I just wanted to know what salt to use.

In the first article you write that "saltwater brines" are not sea water, and that saltwater brine is lesser

But in the linked recipe article, you write to make up essentially a saltwater brine, with Morton's Iodized Salt

Reason for my question regarding using the Sea Salt instead, with the understanding that it would mix up closer to a sea water sample than a saltwater brine

http://reefkeeping.com/issues/2004-06/rhf/index.htm

I have bought 3 different liquid calibration fluids, and they are all different from each other. I'm done doing that

It would be nice if there were some pharmaceutical grade powder, say #SS-PH7.0-35PPT, that one could buy. That it is the same stuff in 2004 as it is in 2024. And be more assured as to the precision of the calibration solution

Ps, I wonder if Rite Aid is giving you a birddog because of your link to their coupon page

 

[Randy Holmes-Farley Verified Community Expert]

I would weigh it out the salt long before I would measured volume

How would one account for the air between the crystals of salt?

Even weighing the water makes more sense for me. Who is to say that a 2 L bottle from when you wrote the articles is the same size as now

35g salt to 965g water just seems easier and more precise in my kitchen to do

I just wanted to know what salt to use.

In the first article you write that "saltwater brines" are not sea water, and that saltwater brine is lesser

But in the linked recipe article, you write to make up essentially a saltwater brine, with Morton's Iodized Salt

Reason for my question regarding using the Sea Salt instead, with the understanding that it would mix up closer to a sea water sample than a saltwater brine

http://reefkeeping.com/issues/2004-06/rhf/index.htm

I have bought 3 different liquid calibration fluids, and they are all different from each other. I'm done doing that

It would be nice if there were some pharmaceutical grade powder, say #SS-PH7.0-35PPT, that one could buy. That it is the same stuff in 2004 as it is in 2024. And be more assured as to the precision of the calibration solution

Ps, I wonder if Rite Aid is giving you a birddog because of your link to their coupon page

Perhaps you misunderstand the standard.

I determined the refractive index of 35 ppt seawater (from scientific articles), determined exactly how much pure sodium chloride is needed in how much water to match that standard (again, from scientific references) and then used a suitably pure source of sodium chloride to make the standard (Morton’s Iodized salt). It is a far, far better way to go than using some sort of seawater mimic and having to worry heavily about moisture in some of the components.

It is, in fact, how the modern salinity scale (PSU) is defined, although that method uses potassium chloride, not sodium chloride.


Any impurities will tend to throw it off, so sea salt cannot be a better source. The known levels of iodine and any other components in the Morton’s are too low to be detectable.

of course mass is the best way to go, even for the water, and have said so hundreds of times. But given the limited precision of most reefing salinity devices, volume is way better than doing nothing. For a given brand of table salt, particle size distributions are not wildly variable.

 

[Ricksofty]

I use a refractometer that is calibrated with calibration solution. I want to get a high-precision hydrometer since those are supposed to be the most accurate

Couldn't you use freshwater and set the line to 0. ?

 

[Reefering1]

Couldn't you use freshwater and set the line to 0. ?

Did you read the thread? That's all that has been discussed here...

 

[CKW]

Update, just read the instructions for my refractometer and the manufacturer suggests calibration using rodi water to zero, it's a D-D one by the way, so it seems I was doing right all along for those instrument.

Hanna salinity checker going on facebook

Well, in my experience once you decide on a”checker “ stay with it. Consistently is more important. You can tweak any checker or reading. Consistency is the most important thing!

 

[BeanAnimal]

…
Never mind

Post was redundant. I replied before I saw Randy’s posts.

 

[YourlocalReefer.]

What do people use that they trust to check l salinity.

Used to use a refractometer albeit calibrated with rodi water on the zero line.

Bought a hanna salinity tester, calibratedcwith their fluid, granted I haven't been as calibrating as regular as I should but just tested the hanna and it was a smidge under 35ppt, calibrated it, tested the tank again and it was 33ppt, re calibrated it and the same result.

Used my old refractometer calibrated to zero with rodi 4x times and got 1.025.

So would you trust a refractometer calibrated to zero or this seemingly untrustworthy hanna item with proper calibration fluid, sensible answer suggests the hanna as im using the proper fluid but I've seen other people say these hanna things are not great.

Thoughts?

I love the hanna salinity checkers but they need calibration a lot.

 

[Dburr1014]

I use a refractometer and calibrate it to a standard. RFH gives you the standard recipe for making it.

I also have my swing arm hydrometer. I use this to make NSW for the AWC. This does get checked periodically and it's always on point.

Nothing wrong with using 2 instruments to check and double check.

Here is a link on why a refractometer can be wrong.

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