Sure glad I got a refractometer

Jayson Ledbetter · Apr 24, 2017

According to my hydrometer I was running my tank at 1.026 and after testing with a refractometer I was actually running at around 1.029

cracker · Apr 24, 2017

I'm happy I replaced my old one. The adjust screw rusted away long ago. Mine was off a couple,3 points also

Maritimer · Apr 24, 2017

Just took delivery of one - looking forward to mixing salt in the upgrade with it!

~Bruce

Mikedawg · Apr 24, 2017

Jayson Ledbetter said:
According to my hydrometer I was running my tank at 1.026 and after testing with a refractometer I was actually running at around 1.029

Ouch! Good thing you checked.

Jayson Ledbetter · Apr 24, 2017

Mikedawg said:
Ouch! Good thing you checked.

no doubt

Adam113 · Apr 24, 2017

Best thing I ever bought for what one costs.

SethOF · Apr 24, 2017

Jayson Ledbetter said:
According to my hydrometer I was running my tank at 1.026 and after testing with a refractometer I was actually running at around 1.029

A refractometer is not necessarily better than a hydrometer. In fact one can state that you are more likely to get an inaccurate reading from a refractometer because of the need for calibration. Also, a refractometer does not measure specific gravity unlike a hydrometer.

Ocean Lotion · Apr 24, 2017

My hydrometer's purpose is to check my hyrometer's accuracy from time to time.

Dsnakes · Apr 24, 2017

I am also glad for that purchase. My hydrometer would read something different every time refilled. Just be sure to keep up with calibration every time, with either distilled or the solution. That's a key to accuracy.

lambchops · Apr 25, 2017

My favorite purchase with reefing has been my milwaukee refractometer, it makes a world of difference.

Randy Holmes-Farley · Apr 25, 2017

Dsnakes said:
I am also glad for that purchase. My hydrometer would read something different every time refilled. Just be sure to keep up with calibration every time, with either distilled or the solution. That's a key to accuracy.

Distilled water will only lead to an accurate measurement if it is a true seawater refractometer, which most used by hobbyists are not.

Randy Holmes-Farley · Apr 25, 2017

SethOF said:
A refractometer is not necessarily better than a hydrometer. In fact one can state that you are more likely to get an inaccurate reading from a refractometer because of the need for calibration. Also, a refractometer does not measure specific gravity unlike a hydrometer.

You could state that, but if you are comparing to plastic swing arm hydrometers, it is probably not correct as hobbyists use the two devices. lol

For a high quality floating glass hydrometer, I agree, they are very often highly accurate.

That said, I prefer conductivity to either method.

Dsnakes · Apr 25, 2017

Randy Holmes-Farley said:
Distilled water will only lead to an accurate measurement if it is a true seawater refractometer, which most used by hobbyists are not.

That is good to know, perhaps I should stick to the calibration fluid. I was unaware of that. Mine is definitely not a fancy one!

SethOF · Apr 25, 2017

Randy Holmes-Farley said:
You could state that, but if you are comparing to plastic swing arm hydrometers, it is probably not correct as hobbyists use the two devices. lol

For a high quality floating glass hydrometer, I agree, they are very often highly accurate.

I think the statement that hobby grade refractometers are more accurate than hobby grade hydrometers is probably correct.

Randy Holmes-Farley said:
That said, I prefer conductivity to either method.

What is your opinion on the Apex conductivity probe?

Randy Holmes-Farley · Apr 25, 2017

SethOF said:
I think the statement that hobby grade refractometers are more accurate than hobby grade hydrometers is probably correct.

Plastic swing arm hydrometers? Probably. Floating glass hydrometers? No. And that assumes that the refractometer is being calibrated correctly. Many people mistakenly use RO/DI or distilled water on a brine refractometer so get inherently incorrect results in seawater.

FWIW, I tested a variety of hydrometers here. The Tropic Marin floating glass hydrometer was quite accurate.

Chemistry and the Aquarium: Specific Gravity: Oh How Complicated! ? Advanced Aquarist | Aquarist Magazine and Blog
http://www.advancedaquarist.com/2002/1/chemistry

from it:

"So how do these hydrometers measure up? In my tank the water was measured to be S=35 ± 0.5 by conductivity. Using the Deep Six swing arm hydrometer I got readings of S=32.5 ± 0.5 at 81 °F and S=32 ± 0.5 at 68 °F. Using the SeaTest I got S=34.5 ± 0.5 at 81 °F and S=34 ± 0.5 at 68 °F.

For the standard type Tropic Marin hydrometer, I got a 77 °F/ 77 °F specific gravity of about 1.0265 ± 0.0003 (Figure 4), which compares well to the expected value of 1.0264."

Figure 4. A Tropic Marin hydrometer showing the meniscus rising to about 1.0260, but the actual reading is about 1.0265.

Randy Holmes-Farley · Apr 25, 2017

SethOF said:
What is your opinion on the Apex conductivity probe?

I've not used an Apex, but I have seen some folks with calibration or other issues with them. But I assume most folks use them just fine. I generally used an old Orion model 128 conductivity meter and probe (expensive but with 4 electrodes for better accuracy and stability), and a Pinpoint.