Thoughts: Hydrometer vs. Refractometer?

[Paul B]

Mine was way off as you can see by where the arm is resting. According to the numbers on it the arm is supposed to be in the center but it is about half an inch off. Who cares? It is always half an inch off so you put a line on it where it is supposed to be and your done. Take the rest of that money that you saved on that refractometer and go out to dinner. Salinity doesn't have to be exact or even close to exact.

 

[Randy Holmes-Farley Verified Community Expert]

I've always used hydrometers in the past, because I was too cheap to buy a refractometer, but I'm realizing that a refractometer just isn't all that expensive and that extra precision might be really valuable. What do you all think?

I prefer conductivity to either a refractometer or a hydrometer, but all of them can work well if you have a quality calibrated instrument, and poorly if you do not.

 

[KrisReef]

I prefer conductivity to either a refractometer or a hydrometer, but all of them can work well if you have a quality calibrated instrument, and poorly if you do not.

A little background for my question: 30 Years ago I routinely used a portable conductivity meter in seawater, and the results it returned did not seem very reliable back then.

What conductivity instrument are you using Randy Holmes-Farley that you prefer that to these other options? I'm not doubting the reported results, just wondering if there are now available hobby grade probes that will perform reliably or if you were speaking about some cool, but totally out of my reach conductivity measuring option that is available to lucky laboratory guys like yourself?

I'm still gonna keep my plastic salinity gadget, but I do try to keep up with the available options for the hobby users.

Thanks -for all you do to support the science end of this hobby!

 

[Scotty Buttons]

Ive always used a hydrometer, kept my water at 1.026 and thought they were ok. When I finally got a refractometer I calibrated it and tested my water, it was at 1.030! The hydrometer was off by quite a bit. The refractometerat BRS sells is only like 35 bucks and comes with calibration solution. It's well worth the money.

 

[Randy Holmes-Farley Verified Community Expert]

A little background for my question: 30 Years ago I routinely used a portable conductivity meter in seawater, and the results it returned did not seem very reliable back then.

What conductivity instrument are you using Randy Holmes-Farley that you prefer that to these other options? I'm not doubting the reported results, just wondering if there are now available hobby grade probes that will perform reliably or if you were speaking about some cool, but totally out of my reach conductivity measuring option that is available to lucky laboratory guys like yourself?

I'm still gonna keep my plastic salinity gadget, but I do try to keep up with the available options for the hobby users.

Thanks -for all you do to support the science end of this hobby!

My main meter is an old Orion model 128 with a 4 electrode probe. Some folks find them on ebay. Great instrument. It reads both salinity and temp in real time, which is great for things like acclimation or dissolving limewater.

I've also udes the Pinpoint salinity meter and it worked fine. It took longer to acclimate to the water temp than the Orion did. It also does show the measured temp (although it must be measuring it).

 

[tiggs]

I personally use a combination of a conductivity probe and refractometer, which I calibrate monthly with both 35pt solution and distilled water. Refractometers used to be $100+ years ago, but they've come down in price quite a bit in recent years. You can get one for $20 on Amazon (or $35 for the same exact one on BRS if you prefer to have it rebranded with their company name on the side). My conductivity probe I rely on more to watch for changes in salinity rather than accurate one time measurements.

One thing worth mentioning with a conductivity probe is to make sure it handles temperature compensation or else your readings will change with tank temperature. Granted, most modern conductivity probes handle this by default.

 

[Todd Kellley]

$5.00 Swing arm hydrometer all the way. To calibrate it I go to where my fish were collected, jump in the water with it and draw a line where the thing sits. Then I am good to go.

Your LFS is a lagoon? I love it! Talk about fresh livestock! Very envious my friend.

 

[hart24601]

$5.00 Swing arm hydrometer all the way. To calibrate it I go to where my fish were collected, jump in the water with it and draw a line where the thing sits. Then I am good to go.

I am saving up for the plane trips to the various locations my coral have been collected to mark each on my refractometer. Who knew calibrating these things could be so expensive!!!

 

[Medic58]

I thought a refractometer was a reefer prerequisite.

 

[EMeyer]

I think conductivity meters are best. But IMO unless you're calibrating your instrument regularly (daily-weekly) the number it's giving is probably wrong, regardless of instrument.

that said, I prefer conductivity because it seems to be less affected by temperature, and its easier and more precise to read a digital number than mess around with focusing perfectly on a refractometer line.

Glass hydrometers are nice and stable but you cant calibrate them. So highly reproducible but IME can be inaccurate.

IME Swing arm hydrometers are so variable I think I would trust my ability to guess salinity by taste more than them But perhaps others have had different experiences with them.

 

[brandon429]

I will never need to own a refract. an oceanic hydrometer I have that is so old there's only a scratch mark for .023 tests as true mark .024 any time I test it against a calibrated refract from lfs. ergo, for ten bucks ten years ago my salinity is set no calibration needed. I think if I started keeping basket stars I'd upgrade to exacting specific gravity, but for the next decade this old swingarm w be fine.

 

[Rick.45cal]

Yeah...it's possible they were more expensive back when I first priced them, which was many years ago, but I had this recollection of them being more in the $100-$150 range. Which still isn't a huge amount of money but it's a lot more than most hydrometers.

They’ve become affordable since their introduction to the hobby. I remember them being ridiculously expensive in the 90’s. I was a little surprised how inexpensive they’ve become. I’ve been a big fan of the Vee Gee refractometer I picked up, I like it as much as my digital milwaukee refractometer. It’s more consistent than the milwaukee is.

 

[rkpetersen]

that said, I prefer conductivity because it seems to be less affected by temperature, and its easier and more precise to read a digital number than mess around with focusing perfectly on a refractometer line.

Digital refractometers are great. Generally hold their calibration well and much easier to use than manual ones.