High Quality Refractometer Recommendations?

[BeanAnimal]

Yup, but good to have another outside source to check the measurement against.

Certainly! Just wanted to make sure that folks understand that they check salinity the same way that we do, and that “ICP” doesn’t do it.

In the last year I have done ICPs with ATI, ReefLab, and Fauna Marin and all salinity measurements lined up with the VeeGee.

Then whatever method you are using to calibrate your VeeGee and the unit itself are working well for you.

I have a bunch of Modern Reef ICP-MS sitting around but won’t use it until after my upcoming tank swap.

I don’t know what that is. Competitor to Oceamo?

 

[BeanAnimal]

If you want a real instrument, then get a multi volt meter and use conductivity readings.

In theory yes, but an EC meter takes into account many variables to provide a calibrated measurement. A DIY set up with a meter and an off-the-shelf or DIY probe is going to require a lot of work and a translation table. The raw meters results are not going to be linear with EC changes in the sample.

 

[Subsea]

In theory yes, but an EC meter takes into account many variables to provide a calibrated measurement. A DIY set up with a meter and off-the-shelf or DIY probe is going to require a lot of work and a translation table, as the results are not going to be linear with EC changes in the sample.

Is EC meter the same as a volt meter set to measure conductivity?

Are you saying that conductivity meter and specific gravity refractor are not linear?

PS: So I googled it

Key Differences in Salinity Measurement

• Accuracy vs. Interference: Conductivity is considered more reliable for pure salt concentration because it is not affected by non-conductive materials like sugar or organic waste, which will increase a refractometer's reading.
• Measurement Range: Some conductivity probes (like those for TDS/multimeters) are designed for low ranges (0–10 ppt) and may require diluting seawater (typically 35 ppt) to get an accurate reading. Refractometers can typically handle high concentrations (up to 28%) without dilution.
• Hobbyist vs. Scientific Use: For most aquarium hobbyists, Refractometers are the popular "gold standard" because they are durable, relatively inexpensive, and provide a quick visual reading. Conductivity meters are often more expensive but offer "hands-free" continuous monitoring.
  
  
  humble.fish +7

Using a Standard Multimeter
Note that a standard household multimeter is generally not suitable for direct salinity measurement unless it is specifically designed for conductivity (EC). Standard multimeters measure resistance (Ω), and while you can mathematically convert resistance to conductivity, the lack of dedicated probes and built-i

 

[diverjm]

Okay, let me rephrase that. What would you use to measure salinity??? @BeanAnimal

 

[BeanAnimal]

Is EC meter the same as a volt meter set to measure conductivity?

Are you saying that conductivity meter and specific gravity meter are not linear?

Same principle yes, but a high end DVM with a dedicated conductivity mode is still going to be inferior in most cases to an EC meter and conductivity probe.

The linearity comment was in regard to using a standard DVM to try and measure conductivity. The dedicated EC meter has compensation built in to account for the probe profile. So, electrode distances, shape, size, etc.

 

[Subsea]

I use a cheap refractometer and check it against a known solution.

 

[BeanAnimal]

Okay, let me rephrase that. What would you use to measure salinity??? @BeanAnimal

I would use two devices of different brands and/or types.

I would calibrate both with Randy’s standard.

I would then compare my tank water readings with both calibrated devices. If they match, great! I now know that they both can be trusted. If they don’t match then I need to decide which is correct. Maybe with a third device, or live knowing the delta between the two and compensate as needed.

What I would not do:
1 - trust any non ASTM lab grade calibration fluid.
2 - calibrate with RO water
3 - trust a single device blindly

Me personally? I have a TM precision hydrometer. I verified its accuracy with Randy’s standard. I measure tank water with it, set (2) refractometers to match it exactly and my GHL conductivity to match. They all reference each other. When they no longer match. I take a hydrometer reading of the tank water then match them again to the tank water. Hope that makes sense.

All of that said, I don’t test salinity very often. May once every month or three to see the EC prove matches the refractometers.

One day if I find a deal on a lab grade EC, I will purchase one of those also.

I don’t care that salinity drifts over a fairly broad range. What I do care about is knowing that what I am reading is accurate.

 

[slingfox]

I have a bunch of Modern Reef ICP-MS sitting around but won’t use it until after my upcoming tank swap.

I don’t know what that is. Competitor to Oceamo?

Modern Reef is a Germany-based reefing supplements company. They just launched in the US in December 2025. They have have very competitively priced ICP testing so I bought a bunch during their launch sale. I will at some point run their test head-to-head against the ATI ICP-MS but not anytime in next few months since I am about to do a full tank transfer and will need to wait until things settle post-transfer.

 

[Subsea]

I would use two devices of different brands and/or types.

I would calibrate both with Randy’s standard.

I would then compare my tank water readings with both calibrated devices. If they match, great! I now know that they both can be trusted. If they don’t match then I need to decide which is correct. Maybe with a third device, or live knowing the delta between the two and compensate as needed.

What I would not do:
1 - trust any non ASTM lab grade calibration fluid.
2 - calibrate with RO water
3 - trust a single device blindly

Me personally? I have a TM precision hydrometer. I verified its accuracy with Randy’s standard. I measure tank water with it, set (2) refractometers to match it exactly and my GHL conductivity to match. They all reference each other. When they no longer match. I take a hydrometer reading of the tank water then match them again to the tank water. Hope that makes sense.

All of that said, I don’t test salinity very often. May once every month or three to see the EC prove matches the refractometers.

One day if I find a deal on a lab grade EC, I will purchase one of those also.

I don’t care that salinity drifts over a fairly broad range. What I do care about is knowing that what I am reading is accurate.

What I get from this thread is summarized in your last sentence:

“I don’t care that salinity drifts over a fairly broad range. What I do care about is knowing that what I am reading is accurate.“

Considering that I use evaporation to cool my tanks, I expect salinity to fluctuate. When specific gravity gets 1.028, I dilute with RODI down to 1.025.

An expensive instrument to measure salinity does not compute when a calibrated hydrometer is dependable enough. For me, the juice ain’t worth the squeeze.

 

[BeanAnimal]

What I get from this thread is summarized in your last sentence:

“I don’t care that salinity drifts over a fairly broad range. What I do care about is knowing that what I am reading is accurate.“

Considering that I use evaporation to cool my tanks, I expect salinity to fluctuate. When specific gravity gets 1.028, I dilute with RODI down to 1.025.

An expensive instrument to measure salinity does not compute when a calibrated hydrometer is dependable enough. For me, the juice ain’t worth the squeeze.

Yep - and without getting into the difference between repeatability and accuracy... The goal for me is know that when I read 1.025 today and 1.025 next week, they are both the same value. The added knowledge that they are actually 1.025 is wonderful as well, but for me it is about know what I am measuring is the same every time.

 

[diverjm]

Appreciate the response. I guess I feel that consistency is the key. I know and use an exact weight for my salt mix per 5 gal mixed and my refractometer confirms the reading on both newly mixed salt and the aquarium, therefore I trust it’s accurate. Or at least consistent with how inaccurate it was new.

 

[BeanAnimal]

Appreciate the response. I guess I feel that consistency is the key. I know and use an exact weight for my salt mix per 5 gal mixed and my refractometer confirms the reading on both newly mixed salt and the aquarium, therefore I trust it’s accurate. Or at least consistent with how inaccurate it was new.

I would suggest using Randy’s standard as a sanity check.

I personally don’t worry about consistency in context to average salinity level, but I do want to know that when I measure, that my reading is consistent so that my decision one way or the other is accurate,

 

[Randy Holmes-Farley Verified Community Expert]

Using a Standard Multimeter
Note that a standard household multimeter is generally not suitable for direct salinity measurement unless it is specifically designed for conductivity (EC). Standard multimeters measure resistance (Ω), and while you can mathematically convert resistance to conductivity, the lack of dedicated probes and built-i

The AI is partly missing the mark, not surprisingly.

Conductivity meters ALWAYS use a high frequency AC voltage/resistance (typically 1 kHz to 3 kHz) to avoid many chemical problems that would occur at the electrode if one kept driving ions in the same direction.

A DIY cannot use a simple volt meter and expect accurate results.

 

[Aspect]

Bump for those using the MA887 is there anyway to calibrate with 35 ppt solution or only rodi? Even with rodi it reads my refracto juice and brightwell aquatics solution at 1.026 so it appears to truly be a seawater refractometer

 

[Ryanliyikun]

The Hanna Salinity Tester is super easy to use and gives quick, reliable readings. Simple setup, consistent results, and a solid choice if you want accurate salinity measurements without hassle.

 

[mcarroll]

I've bought 3 from Amazon and they all need recalibrated within a few days. I'll check out the BRS one thanks

It's too bad nobody shops at LFS's or uses branded gear anymore...so who knows what you've been buying how how you've been told to use it.

I'm using the same refractometer I bought from Marine Depot almost 20 years ago, which was the same one my LFS carried at the time. It's never needed a recalibration except when the screw was messed with by a child with e screwdriver. Never needed another calibration since then.

There's litereally no reason I can think of why a refractometer would somtaneously lose calibration. But then I didn't build my reef from Amazon parts, I used proven stuff.

I find conductivity meters that have a probe on a cord much more user friendly than either hydrometers or refractometers. :)

Can you recommend some specifics, or at least a good type?

(Ideally one that could be managed by a newb.)

Ugh even this veegee already drifted up an entire ppt in only 24 hours, really surprising for a nearly $200 refractometer. This is beyond frustrating I need to find a new way to find salinity

Sounds like you need a swing arm hydrometer. Stone-age simplicity – foolproof.

If you see bubbles in your sample, shake them out....there is no other thing to do other than rinse the unit well after use.

You can calibrate it for better accuracy (ie if you use hyposalinity in fish treatment), but they are usually pretty accurate to begin with – plenty accurate for daily reef use!!

I believe the RODI calibration sets the unit to true zero without any salinity present. All I can say is I just did an ICP test and my salinity matched exactly to what the refractometer reads.

I don't understand the problem reports on refractometers either. Compared to my experience all of them practically sound fictional. Even the **thoroughly abused** refractometer at the shop I used to work at never needed calibration and it was literally rusty and salt crusted.

IME the refractometer is bomb proof....it's the only thing better than a swing arm hydrometer for everyday use. (...and swing arms are VERY practical, so that's saying something!)

Glass hydrometers are interesting, but most reefers aren't going to keep that around for long without breaking it, and even if they don't, they'll die from worrying about it. LOL ;) But seriously, it is **delicate** lab ware....not for the average Joe or Jolene who has kids and pets running around and other life happening around the tank, etc. AFAIK, this is the whole reason swing-arms were invented. ;)

 

[Randy Holmes-Farley Verified Community Expert]

Bump for those using the MA887 is there anyway to calibrate with 35 ppt solution or only rodi? Even with rodi it reads my refracto juice and brightwell aquatics solution at 1.026 so it appears to truly be a seawater refractometer

Calibrate with the ro/di and then check it with a good 35 ppt. You can manually correct if it is off.

 

[Aspect]

Calibrate with the ro/di and then check it with a good 35 ppt. You can manually correct if it is off.

How do I manually correct it?

 

[Randy Holmes-Farley Verified Community Expert]

How do I manually correct it?

Calibrate it however you want. Then test 35 ppt. If it reads 34 ppt, then you multiply all readings with that calibration by 35/34.

If you use specific gravity, then use the last digits only . For example, 35 ppt is about sg = 1.0264. If it reads 1.025 then multiply all readings by 26.4/25, and put the one in front again.

 

[Randy Holmes-Farley Verified Community Expert]

Can you recommend some specifics, or at least a good type?

(Ideally one that could be managed by a newb.)

High end ones are expensive (hundreds to over a thousand dollars), but are great instruments.

But for years I had both a Pinpoint and an Orion (high end).

Both worked perfectly adequately and seemed to give similar results in most cases, except the Orion came to a final reading much faster (maybe partly due to a faster temperature equilibration and measurement for its internal correction).

https://americanmarineusa.com/collections/pinpoint-monitors/products/pinpoint-salinity-monitor