Average Accuracy of Glass Hydrometers

[AydenLincoln]

The only issue is I'm not in the States and they don't sell it on Amazon...also $35 is a little bit more than I was hoping to spend before shipping

I have a different one I’m not sure the brand though I got it from my work well I took it lol it was not being used. Let me see if I can find it online.

 

[Spare time]

The main advantage of a glass hydrometer is that it is more consistent than anything that needs to be calibrated. Swing arm hydrometers are notoriously unreliable but glass hydrometers are great, provided you know how far out they are (if at all).

I thin the swing arms are (with the exception of the coralife one) accurate if one takes care of it. I've tested several against two freshly calibrated refractometers and they were the same. These ones were well taken care of and had 0 air bubbles (people often don't fill them up correctly). The IO version is my favorite

 

[Tcook]

I have the Tropic Marin and it is very consistent as long as you use it with the correct temperature water or use a correction chart. However, I just assumed it was accurate. Mine is off by 0.0015. So you need to calibrate against a known standard. Too bad they don't calibrate these at the factory. Cost no doubt.

 

[livinlifeinBKK]

I have the Tropic Marin and it is very consistent as long as you use it with the correct temperature water or use a correction chart. However, I just assumed it was accurate. Mine is off by 0.0015. So you need to calibrate against a known standard. Too bad they don't calibrate these at the factory. Cost no doubt.

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

 

[livinlifeinBKK]

I might be better off just buying some calibration fluid with a good rating on Amazon for my refractometer and have it shipped here...that would be a lot cheaper and probably just as accurate

 

[Sump Crab]

funny this thread popped up because I literally just ordered the tropic Marin glass hydrometer yesterday lol.

I had a tank emergency while out of town and had my mother in law let in an aquarium maintenance guy to fix the issue. Besides what he had to fix he also told me that my salinity was low, like 1.021 or something. He said that was according to his Hanna checker and refractometer. I thought this was odd as I use a calibrated refractometer myself. I figured that the Calibration fluid went bad or perhaps even my refractometer. When I got home I ordered new calibration fluid, recalibrated my refractometer and then tested my tank water which measured 1.026! Now my mind is all messed up lol. Then I went and bought an instant ocean hydrometer and it also said 1.025 or 6! So as the final test I decided to try out the tropic Marin, it will be here Thursday.

I may need to tell the maintenance guy to recalibrate his tools! We will see.

 

[davidcalgary29]

The only issue is I'm not in the States and they don't sell it on Amazon...also $35 is a little bit more than I was hoping to spend before shipping

Believe me, I was in the same boat until a kind soul here on this site came to the rescue and sold me his spare. I agree that they're pricey, but they're totally worth the money.

 

[davidcalgary29]

I might be better off just buying some calibration fluid with a good rating on Amazon for my refractometer and have it shipped here...that would be a lot cheaper and probably just as accurate

That's a must for any refractometer. I have two or three bottles of calibration fluid, and check monthly. I fully admit to the neurosis that I have developed after the beerfractometer incident.

 

[EeyoreIsMySpiritAnimal]

Oh okay I’ve never used one. But I know it can depend on the exact one being used. I have a saltwater one and I did say theoretically but I’d definitely go with a saltwater one. I believe there are some other food grade ones that could work though. As it’s not just used in beer/winemaking. I just have heard of people using ones that are also for food/drinks.

No, no, no, and no.
You need to use one intended for brine or saltwater.

 

[livinlifeinBKK]

Believe me, I was in the same boat until a kind soul here on this site came to the rescue and sold me his spare. I agree that they're pricey, but they're totally worth the money.

Idk how to order one if it's not on Amazon though...I've looked into BRS international shipping and they say they offer it but at checkout it doesn't show up

 

[AydenLincoln]

I think it’s this one or another similar brand…it’s one of those things being as they all look the exact same that they probably are made by the same company and sold under different names. It’s $3 I’ve seen another one that looks the exact same for $7 but regardless they both look exactly the same as mine and have the same materials. https://a.co/d/goxsgg4

 

[EeyoreIsMySpiritAnimal]

Randy has a "recipe" for homemade calibration solution in the reef chemistry forum.
I also have the Tropic Marin glass hydrometer and recommend it. However, any similar product that's got decent reviews should serve your purpose -- as noted, just start off measuring it against a known accurate value (i.e. a properly calibrated refractometer), note any difference, and then take that into account during future use.
The good thing about the sealed glass ones is they don't need to be recalibrated.

 

[exnisstech]

Ditto to Randy's recipe. Used regular table salt. I made a batch and compared to a calibration fluid I had been using and it was spot on

 

[livinlifeinBKK]

Randy has a "recipe" for homemade calibration solution in the reef chemistry forum.
I also have the Tropic Marin glass hydrometer and recommend it. However, any similar product that's got decent reviews should serve your purpose -- as noted, just start off measuring it against a known accurate value (i.e. a properly calibrated refractometer), note any difference, and then take that into account during future use.
The good thing about the sealed glass ones is they don't need to be recalibrated.

I really like the idea of the glass hydrometer but the Tropic Marin one isn't available anywhere I can find since I'm not in the States which leaves me with other options on Amazon but people aren't personally vouching for them because they haven't used them. Also, if I don't go with the Tropic Marin one (I don't know how I can) or a really expensive individually calibrated one I found on Amazon I have to buy the calibration fluid anyway to test for deviations so I might as well just go with the calibration fluid for now because why would I need a well calibrated refractometer and a hydrometer at the same time?

 

[EeyoreIsMySpiritAnimal]

I really like the idea of the glass hydrometer but the Tropic Marin one isn't available anywhere I can find since I'm not in the States which leaves me with other options on Amazon but people aren't personally vouching for them because they haven't used them. Also, if I don't go with the Tropic Marin one (I don't know how I can) or a really expensive individually calibrated one I found on Amazon I have to buy the calibration fluid anyway to test for deviations so I might as well just go with the calibration fluid for now because why would I need a well calibrated refractometer and a hydrometer at the same time?

I understand that you're not able to get the TM one, I was just mentioning that I have one.
I have not looked on Amazon; I imagine there are ones there with good reviews but I could be wrong
The reason to get a glass hydrometer as well as the calibration fluid is, assuming you're careful and it doesn't break, once you know the correct variance (if any) of the hydrometer, then you can use it forever. At some point, any bottle of calibration solution will need to be replaced...

 

[Reef.]

I really like the idea of the glass hydrometer but the Tropic Marin one isn't available anywhere I can find since I'm not in the States which leaves me with other options on Amazon but people aren't personally vouching for them because they haven't used them. Also, if I don't go with the Tropic Marin one (I don't know how I can) or a really expensive individually calibrated one I found on Amazon I have to buy the calibration fluid anyway to test for deviations so I might as well just go with the calibration fluid for now because why would I need a well calibrated refractometer and a hydrometer at the same time?

I personally wouldn’t buy a calibration fluid, I would make my own, I’ve seen reports on here of different reading from 2 different bottles,of calibration fluid, it would just be as cheap to buy a 0.01g scale of Amazon than to buy the calibration fluid and not know if it’s at the correct salinity.

 

[Reef.]

I have the Tropic Marin and it is very consistent as long as you use it with the correct temperature water or use a correction chart. However, I just assumed it was accurate. Mine is off by 0.0015. So you need to calibrate against a known standard. Too bad they don't calibrate these at the factory. Cost no doubt.

That is quite a lot, did you make your own calibration fluid? If so, how do you know it wasn’t your scales or your thermometer, that was off?

I checked mine and it seemed near enough spot on.

 

[Tcook]

That is quite a lot, did you make your own calibration fluid? If so, how do you know it wasn’t your scales or your thermometer, that was off?

I checked mine and it seemed near enough spot on.

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.

 

[livinlifeinBKK]

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.

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

 

[gbroadbridge]

Ok so it's really been bothering me for a while that I don't know exactly where my salinity stands (I think it might be up to 3ppt off which would be detrimental for the starfish) so I was thinking about getting a glass hydrometer but where I am the Tropic Marin hydrometer isn't available and I wouldn't want to pay $35 for it anyway because I know every scientific instrument has standard error. My question is just how accurate is the average glass hydrometer? Does anyone use one other than the Tropic Marin one?

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.