Average Accuracy of Glass Hydrometers

[livinlifeinBKK]

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?

 

[davidcalgary29]

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?

Yes. I bought this glass hydrometer off of Amazon, and it was off about 2 ppt. It's also somewhat hard to read. Then again, it's much more compact and easy-to-use than the Tropic Marin beast, which requires a wheelie bin or other large container due to its large size.

I think that these mini hydrometers are fine as long as you can back it up with an accurate refractometer -- and remember how far it's off in its readings. I find that it's just much faster to use a refractometer, even with its need for occasional recalibration.

 

[AydenLincoln]

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.

 

[GobyGuy]

I was on the phone w the lfs today asking for a refractometer / they had hydrometers but also claimed they were unreliable / inaccurate I don’t what brand it was though

 

[livinlifeinBKK]

I was on the phone w the lfs today asking for a refractometer / they had hydrometers but also claimed they were unreliable / inaccurate I don’t what brand it was though

They call the plastic ones you fill with water hydrometers too which is probably what they were talking about

 

[livinlifeinBKK]

And thanks guys, I was hoping to hear they were all generally really accurate though because of how they work...I guess it does take some precision to make a really accurate one though

 

[AydenLincoln]

They call the plastic ones you fill with water hydrometers too which is probably what they were talking about

Yes very important for it to be glass not the plastic kind.

 

[livinlifeinBKK]

Yes very important for it to be glass not the plastic kind.

Yeah I know...I'd never trust the plastic ones...one tiny air bubble will throw it way off but I wouldn't even expect it to be accurate without a single bubble

 

[SamsReef]

I always keep the plastic hydrometer as a backup. It’s very easy to get all bubbles out and to lay it on flat surface to get accurate reading.

Sam

 

[firechild]

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).

 

[davidcalgary29]

…though a beer one could theoretically work.

If you're talking about a beerfractometer, don't do that. I speak from personal experience! I raised my SG to over 1.037 with one (bought off Amazon by mistake) and fried a Kenya Tree.

 

[AydenLincoln]

If you're talking about a beerfractometer, don't do that. I speak from personal experience! I raised my SG to over 1.037 with one (bought off Amazon by mistake) and fried a Kenya Tree.

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.

 

[livinlifeinBKK]

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).

Yeah, that's why I was actually thinking about buying a glass hydrometer instead of calibration fluid for my refractometer since for some reason there aren't many calibration fluids available here and hydrometers would actually be about the same price (but I want accuracy if I go that route otherwise it defeats the purpose)

If you're talking about a beerfractometer, don't do that. I speak from personal experience! I raised my SG to over 1.037 with one (bought off Amazon by mistake) and fried a Kenya Tree.

No haha, I know the difference...there are actually way more hydrometers for alcohol than salinity for sale but since alcohol has a different density it wouldn't work right

 

[davidcalgary29]

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.

Well you can use one: it will give consistent readings, but they'll be consistently off by a very large margin, and you always have to keep that in mind if using it. It took me a while to figure out that that unit was off by at least 12 ppt for saltwater reading. I put mine far, far away as I didn't want to make another catastrophic mistake with it.

 

[AydenLincoln]

Well you can use one: it will give consistent readings, but they'll be consistently off by a very large margin, and you always have to keep that in mind if using it. It took me a while to figure out that that unit was off by at least 12 ppt for saltwater reading. I put mine far, far away as I didn't want to make another catastrophic mistake with it.

True! It also depends on the scale that’s on it. If it seems to have a saltwater scale or being 20-40 ppt. or having 1.026 on it vs something like 100-500 then that wouldn’t work.

 

[AydenLincoln]

And I know only part of this article is free but it explains some info: https://study.com/academy/lesson/hydrometer-definition-scales-uses.html

 

[livinlifeinBKK]

The frustrating thing about hydrometers is that temperature matters and can affect the reading

And I know only part of this article is free but it explains some info: https://study.com/academy/lesson/hydrometer-definition-scales-uses.html

Thank you Ayden, I actually know how to use them and everything, I was just wondering what people's experience with different brands were and if they were all very accurate because if I buy an inexpensive one I just wasted money if it isn't reliable

 

[davidcalgary29]

The only glass hydrometer that I have (or have used) that's been completely accurate (within my ability to cross-check it with three different refractometers and a swing-arm hydrometer) is the Tropic Marin. Every other one has been off a bit, even if not by that much in the end.

 

[afrokobe]

The tropic marin one is:

• Maximum deviation: 0.001 at 77° F (25° C)

High Precision Hydrometer

Ensure that your equipment is reading correctly and your aquarium is at the right salinity with Tropic Marin's High Precision Hydrometer. Many tank inhabitants are sensitive even to minor changes of the water conditions. Unfortunately as we've all experienced, salinity reading equipment as...

www.bulkreefsupply.com

I do agree its quite cumbersome to store due to its large size, but its not terrible to use. I toss it in the sump (with return off) if i need to check the tank salinity and in whatever container I am mixing salt in.

 

[livinlifeinBKK]

The only glass hydrometer that I have (or have used) that's been completely accurate (within my ability to cross-check it with three different refractometers and a swing-arm hydrometer) is the Tropic Marin. Every other one has been off a bit, even if not by that much in the end.

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