Average Accuracy of Glass Hydrometers

[Tcook]

It doesn't surprise me that there are slight differences among calibration fluids, after all practically everything has a standard error (everything mass produced)... the best an average Joe can do is compare as many replicates as possible and accept the most common as being closest to correct...with that said, why not just get a precise scale with really good reviews off Amazon because his scale is unlikely to match yours perfectly even if it's the exact same model

Just ordered one. Hopefully will have this hydrometer calibrated by Friday.

 

[gbroadbridge]

They actually have individually calibrated ones on Amazon but I'm not about to pay what that price (really expensive)

Salinity is one of the most important things to get right.

$35 is cheap compared to the cost of everything else in this hobby.

You should think about spending $100. It's a cheap investment in a tank that will end up costing thousands.

 

[livinlifeinBKK]

Hydrometers can be accurate if you use them correctly and remember that you need to do manual temperature compensation.

The gold standard are conductivity meters, but they need frequent calibration. Having said that you can make a DIY calibration solution for pennies.

Yeah from what I know they can be the most accurate, but there's still gonna be a standard error if they were mass produced now that I think about it...like i was saying before, the most commonly accepted to be correct is the Tropic Marin which I can't get sent here so I have to get a different one, make my own calibration fluid since people don't seem to trust it, and take that as accurate to find the error in whatever hydrometer I get

Just ordered one. Hopefully will have this hydrometer calibrated by Friday.

I literally just ordered one myself! I got a 100 gram with .01 precision...I was gonna get .001 precision since I need it for my study as well but every professor I've spoken to says .01 is precise enough.

 

[livinlifeinBKK]

Just ordered one. Hopefully will have this hydrometer calibrated by Friday.

Here's the one I got +-.03 gram accuracy, weighs to the nearest .01 gram and comes with a 50 gram weight to calibrate it which I like...should be as good as any other that weighs to the nearest .01 (or good enough at least)

https://shopee.co.th/product/377606248/17180487066?smtt=0.281183761-1661930505.9

 

[Randy Holmes-Farley Verified Community Expert]

They are super accurate and good because it’s simply using density to tell what the salinity is a tried and true formula/principle whatever you want to call it. Plus they are widely used in a variety of resources assuming you got a saltwater hydrometer…though a beer one could theoretically work. And bonus they don’t have to be calibrated so it’s virtually human error proof besides the risk of breaking it. I have one. Look at Amazon they are relatively inexpensive too.

Every statement you made about hydrometers, except calibration (which is a double edged sword: doesn’t need calibrated = cannot be calibrated) is equally true of conductivity meters and refractometers.

You are seemingly asserting that these other methods do not have a tried and true formula to relate the property measured to salinity? That is not true.

it is also not true that they are not used widely in other settings. Chemistry labs far more often use conductivity meters than hydrometers (I’ve never seen one in a lab I worked in).

The modern PSU salinity scale is actually defined by conductivity since it is the most readily reproducible and accurate method for measuring salinity.

Does that mean every device sold to hobbyists, no matter how cheaply made, is accurate? Of course not.

 

[Randy Holmes-Farley Verified Community Expert]

I have yet to see anyone do a study of the average accuracy of the Tropic Marin hydrometer, and I think that would be interesting to see.

The small TM version that I had was adequately accurate to within my ability to distinguish the actual reading. But, IMO, folks shouldn’t assume they are accurate without checking.

 

[Homey D. Clownfish]

Yeah from what I know they can be the most accurate, but there's still gonna be a standard error if they were mass produced now that I think about it...like i was saying before, the most commonly accepted to be correct is the Tropic Marin which I can't get sent here so I have to get a different one, make my own calibration fluid since people don't seem to trust it, and take that as accurate to find the error in whatever hydrometer I get

I literally just ordered one myself! I got a 100 gram with .01 precision...I was gonna get .001 precision since I need it for my study as well but every professor I've spoken to says .01 is precise enough.

I recommend getting a plastic 500 ml graduated cylinder to measure it in. It will be easier to read and you won’t have to worry about the glass breaking inside your sump or tank.

 

[AydenLincoln]

Every statement you made about hydrometers, except calibration (which is a double edged sword: doesn’t need calibrated = cannot be calibrated) is equally true of conductivity meters and refractometers.

You are seemingly asserting that these other methods do not have a tried and true formula to relate the property measured to salinity? That is not true.

it is also not true that they are not used widely in other settings. Chemistry labs far more often use conductivity meters than hydrometers (I’ve never seen one in a lab I worked in).

The modern PSU salinity scale is actually defined by conductivity since it is the most readily reproducible and accurate method for measuring salinity.

Does that mean every device sold to hobbyists, no matter how cheaply made, is accurate? Of course not.

That was not my intention I never meant to bash refractometers….I’m sorry you assumed that. I just mean they can be used for other things and are used in other industries I’ve definitely seen them used in beer/winemaking for personal use because there’s different types of hydrometers of course they are used most commonly in this hobby and of course like any testing in this hobby it can “potentially” be off. But the simple method used is tried and true. OP asked about hydrometers and the accuracy and I shared what I know. I also think it’s just a good idea to test salinity against another method too regardless to verify…I do that’s how I know the one I have is right.

 

[KStatefan]

If you happen to fine one in Bangkok be aware that Tropic Marin makes two different models one that measures specific gravitity and one that measures density.

 

[Reef.]

Hydrometers can be accurate if you use them correctly and remember that you need to do manual temperature compensation.

The gold standard are conductivity meters, but they need frequent calibration. Having said that you can make a DIY calibration solution for pennies.

Reading all the reviews on the Hanna salinity checker, they do t seem gold standard to me.

 

[Reef.]

Checked at my lfs against their hydrometer and calibration fluid. I also have heard many complaints about these fluids. I think BRS may have done a video on it. What scale do you use? I'd like to make my own cal fluid.

I just picked up a precision scale from Amazon, no brand, seems very accurate, but could very well be slightly out, My thermometer is certified to within 0.1c, the thermometer plays a big part, the average thermometer can be out over 1 degree, that’s why I think it’s hard to say it’s your hydrometer that is out as much as you said it was, when it could be the scale,or thermometer.

 

[livinlifeinBKK]

Reading all the reviews on the Hanna salinity checker, they do t seem gold standard to me.

I've definitely read some negative reviews about them as well...I think it's safe to say any salinity measuring device needs to be checked against others and it'll never be perfect due to standard error like I mentioned earlier but some are definitely closer than others... refractometers seem to be the highest rated by far on Amazon. @Randy Holmes-Farley I know you have a method of making a stock 35 PSU solution but I've also heard from a pretty reputable source that one can be made simply from weighing 35 grams of table salt and mixing it into a 1 liter bottle of water as bottled beverages are usually very close to the stated volume (I've heard a 1 liter bottle of alcohol is actually practically exactly 1 liter due to being taxed for every drop of alcohol (of course the liquor bottle would be emptied and filled with RODI water before mixing the salt.) Is that true? Also are salinity refractometer calibration fluids really as unreliable as people have said?

 

[Reef.]

I've definitely read some negative reviews about them as well...I think it's safe to say any salinity measuring device needs to be checked against others and it'll never be perfect due to standard error like I mentioned earlier but some are definitely closer than others... refractometers seem to be the highest rated by far on Amazon. @Randy Holmes-Farley I know you have a method of making a stock 35 PSU solution but I've also heard from a pretty reputable source that one can be made simply from weighing 35 grams of table salt and mixing it into a 1 liter bottle of water as bottled beverages are usually very close to the stated volume (I've heard a 1 liter bottle of alcohol is actually practically exactly 1 liter due to being taxed for every drop of alcohol (of course the liquor bottle would be emptied and filled with RODI water before mixing the salt.) Is that true? Also are salinity refractometer calibration fluids really as unreliable as people have said?

Randy actually gives some alternatives to use, he does even suggest a pop bottle but unless you are making a very large volume, I would stick to scales, you can also pick up some calibration weights at the same time if you want but they too can be out! The margins are so small for error when making the calibration fluid.

https://reefkeeping.com/issues/2004-06/rhf/index.php

 

[livinlifeinBKK]

And for the record, I know salinity is very important so I'm not trying to go the cheapest route or anything but I also know that it'll never be perfect so dropping a large sum of money on a new device when I already have a probe and refractometer ( sure they're off by probably 2-3 PSU or so which is significant) seems a little silly especially considering the fact that evaporation is constant and no ATO will be able to keep salinity absolutely perfect to what you set it to.

Randy actually gives some alternatives to use, he does even suggest a pop bottle but unless you are making a very large volume, I would stick to scales, you can also pick up some calibration weights at the same time if you want but they too can be out! The margins are so small for error when making the calibration fluid.

https://reefkeeping.com/issues/2004-06/rhf/index.php

I actually ordered a scale with a weight for calibration +-.03 gram accuracy and .01 gram precision with a 200 gram max

https://shopee.co.th/product/377606248/17180487066?smtt=0.281183761-1661930505.9

 

[KStatefan]

I've definitely read some negative reviews about them as well...I think it's safe to say any salinity measuring device needs to be checked against others and it'll never be perfect due to standard error like I mentioned earlier but some are definitely closer than others... refractometers seem to be the highest rated by far on Amazon. @Randy Holmes-Farley I know you have a method of making a stock 35 PSU solution but I've also heard from a pretty reputable source that one can be made simply from weighing 35 grams of table salt and mixing it into a 1 liter bottle of water as bottled beverages are usually very close to the stated volume (I've heard a 1 liter bottle of alcohol is actually practically exactly 1 liter due to being taxed for every drop of alcohol (of course the liquor bottle would be emptied and filled with RODI water before mixing the salt.) Is that true? Also are salinity refractometer calibration fluids really as unreliable as people have said?

My Hanna always reads low compared to my hydrometer.

This is the standard i used to verify my Tropic Marin hydrometer.

 

[Reef.]

And for the record, I know salinity is very important so I'm not trying to go the cheapest route or anything but I also know that it'll never be perfect so dropping a large sum of money on a new device when I already have a probe and refractometer ( sure they're off by probably 2-3 PSU or so which is significant) seems a little silly especially considering the fact that evaporation is constant and no ATO will be able to keep salinity absolutely perfect to what you set it to.

I actually ordered a scale with a weight for calibration +-.03 gram accuracy and .01 gram precision with a 200 gram max

https://shopee.co.th/product/377606248/17180487066?smtt=0.281183761-1661930505.9

The scale looks fine. Similar to mine.

We are all aiming for the average sea silinity, what is important is having your silinity as constant as possible, doesn’t matter if your scales or thermometer is slightly out as long as it’s constantly giving the same reading, the fish and corals won’t mind if the water is 1.0264 or 1.0260 as long as it stays constant.

Remember our fish and corals would not all have come from the same area, the silinity would have been different for all of them, depending where they were picked up from.

 

[livinlifeinBKK]

The scale looks fine. So to mine.

We are all aiming for the average sea silinity, what is important is having your silinity as constant as possible, doesn’t matter if your scales or thermometer is slightly out as long as it’s constantly giving the same reading, the fish and corals won’t mind if the water is 1.0264 or 1.0260 as long as it stays constant.

Remember our fish and corals would not all have come from the same area, the silinity would have been different for all of them, depending where they were picked up from.

True, also there are short term variances considering weather and variables such as that.

 

[Reef.]

My Hanna always reads low compared to my hydrometer.

This is the standard i used to verify my Tropic Marin hydrometer.

why do you make so much Lol. I use 3.65 salt and 96.35 water.

 

[Reef.]

True, also there are short term variances considering weather and variables such as that.

And rain.

 

[Reef.]

why do you make so much Lol. I use 3.65 salt and 96.35 water.

Silly me just noticed it’s for a hydrometer p, yeah when I check my hydrometer I make 500ml, with the added benefit that the bigger volume will minimise any weighing and temp errors.