Hydrometer vs Refractometer

[Electrotech]

Ok so I've been using a coralife deep 6 hydrometer since my first tank about 15 years ago, not the same one but the same model. I found a good deal on a used refractometer and bought it. Just tried it out for the first time, I calibrated it first (it was a little off) then checked the water in my 37 and the refractometer says the sg is 1.025 where my hydrometer says 1.022 it's close but it's really at opposite ends of the range, I like to keep it between what I thought was 1.022 minimum and 1.024 maximum.

I'm assuming I should go by what the refractometer says and quit using the hydrometer?

 

[MikeyB]

That's what i would do as long as its calibrated, which you said it was. I made the switch a while back from hydrometer to refracto and make's everything so much easier

 

[Reefing Madness]

Yup, hydrometers are to inaccurate and inconsistent.

 

[tyler1503]

I found hydrometers to be incredibly consistant. Not so much accuracy, but very consistant. The floating glass kind anyway.
I've never had an issue with mine, it's served me well for the last 3 years and is going strong!

 

[Kworker]

IMO refractometers are too inexpensive to skip out on. I never even bothered with hydrometers.

 

[reggaedrummin]

Stick with the refractometer. They should stop selling hydrometers. They are inaccurate. With refractometers so cheap and readily available I cannot understand why anybody wouldn't use one. just make sure to calibrate it often.

 

[pickupman66]

refracto all the way... will never touch a hydrometer again unless to toss it in the trash.

 

[Electrotech]

Cool, thanks for the replies.

 

[Pimentinha1987]

Best thing out there IMO is the Milwaukee electronic refractometer...

Every since I upgraded it's been nothing but a breeze to do water changes.
And to my surprise it stays calibrated for a very long time...

 

[dbl]

Agreed on the Milwaukee Electronic refractometer. Super easy to use (and read) and mine too stays calibrated. But then again, it’s all I’ve ever used.

 

[Randy Holmes-Farley Verified Community Expert]

I calibrated it first (it was a little off) then checked the water in my 37 and the refractometer says the sg is 1.025 where my hydrometer says 1.022 it's close but it's really at opposite ends of the range, I like to keep it between what I thought was 1.022 minimum and 1.024 maximum.

If we are talking about a reef aquarium, I'd suggest that a specific gravity of 1.024 is closer to the bottom of the desirable range, not the top. Typical reef salinities are closer to 34-36 ppt (sg = 1.0256 to 1.0271).

I suggest that folks target the typical ocean average of 35 ppt, which has a specific gravity of 1.0264.

 

[Randy Holmes-Farley Verified Community Expert]

Yup, hydrometers are to inaccurate and inconsistent.

Assuming we are talking about swing arm hydrometers, I agree. But floating glass hydrometers, especially large ones, can be very accurate. Such as the Tropic Marin.

That said, I prefer conductivity meters to both refractometers and hydrometers.

They are easy to use, read in real time (good for acclimating, for example), some read temp as well, can be easily checked for accuracy, and have other reef uses that neither hydrometers nor refractometers do (such as limewater (kalkwasser) potency).

 

[mainereefer]

I use a refractometer to calibrate my hydrometer

 

[Huntor0]

I love using my Milwaukee electronic refractometer but may look into a conductivity meter as well.

 

[msderganc]

Assuming we are talking about swing arm hydrometers, I agree. But floating glass hydrometers, especially large ones, can be very accurate. Such as the Tropic Marin.

That said, I prefer conductivity meters to both refractometers and hydrometers.

They are easy to use, read in real time (good for acclimating, for example), some read temp as well, can be easily checked for accuracy, and have other reef uses that neither hydrometers nor refractometers do (such as limewater (kalkwasser) potency).

Hi Randy - so I just got a Tropic Marin floating hydrometer and it's reading 1.025, whereas my seawater refractometer, calibrated with 35ppt is reading 35ppt.

Which would you believe?

 

[redfishbluefish]

Ok so I've been using a coralife deep 6 hydrometer since my first tank about 15 years ago, not the same one but the same model. I found a good deal on a used refractometer and bought it. Just tried it out for the first time, I calibrated it first (it was a little off) then checked the water in my 37 and the refractometer says the sg is 1.025 where my hydrometer says 1.022 it's close but it's really at opposite ends of the range, I like to keep it between what I thought was 1.022 minimum and 1.024 maximum.

I'm assuming I should go by what the refractometer says and quit using the hydrometer?

You mentioned that you calibrated the refractometer but didn't mention what you used for calibration. It's most accurate if you use 53 mS (35 ppt) calibration fluid to calibrate your refractometer (and not RO/DI water.)

 

[phillrodrigo]

I wonder why the floating ones work well but the swing arms are garbage. I completely agree but they pretty much use the same method just a different in a different way. It's ready gravity so why are the swing arms garbage. I broke my refractometer and went out and bought a swing arm while waiting for my new refractometer to be sent and out of the box it was completely off. It was reading my tank off the chart and rodi water at 1.012