Refractometer vs floating needle

[90addict]

New to the saltwater world. Which would you trust? I calibrated the refractometer last night with distilled water and it read 0

 

[Asm481]

Swing arm is great unless there are any bubbles or any build up from drying, they also need lots of water. Refractometer is best but get some calibration fluid. Distilled is great if you run 0 for salinity! Serious get calibration fluid. Other great reason you only need a couple drops so you can test level on your fish you buy to see how far apart you are for aclimation.

 

[aciak]

Typically you want to use calibration solution for the refractometer. It’s cheap for something as important as salinity. Also, make sure you didn’t get one that’s for measuring beer.

 

[Sophie"s mom]

Refractometer every time for me.

 

[Tamberav]

I would trust the Vee Gee Scientific STX-3 and the High Precision Glass Hydrometer from Tropic Marine and nothing else I guess I trust neither of those.

 

[I never finish anythi]

Refractometer for sure . Calibrate with 35ppt . Randy has a DIY recipe you can easily make at home

 

[KrisReef]

Did anyone else notice that the scale inside the refracto meter is tilted?

I see a bubble on the swingarm in the OP’s foto, fill carefully by calmly emerging it . Read it leveled with the line of the body parallel to the surface of the sample. Rinse with RODI to prevent salt complications

 

[KrisReef]

I would trust the Vee Gee Scientific STX-3 and the High Precision Glass Hydrometer from Tropic Marine and nothing else I guess I trust neither of those.

I’m offended by this precision snobbery against the finest piece of plastic equipment ever invented!

I have travelled with my trusty sea test ultra grade A OG Plastic salt density indicator and have enjoyed repeated validation of it in reefs around the equator.

(It has caused significant frowning from TSA agents looking through my suitcase as they ponder the question; “What is this thing and can it interfere with flight safety?”)

I use it routinely and prefer it to glass tools because the glass can be easily broken while the plastic is amazingly durable.

The other issue with refractometers is that they are heavy and take up space where the frags can fit for the flight home. TSA doesn’t allow calibration solutions in the carryons either.

 

[FernBluffReef]

I much prefer my cheap instant ocean hydrometer. Refractometer is all over the map

 

[90addict]

So I noticed on the box that is says to "season the needle". I've tested 3 more times so far and they have been slowly coming down

 

[Tamberav]

I’m offended by this precision snobbery against the finest piece of plastic equipment ever invented!

I have travelled with my trusty sea test ultra grade A OG Plastic salt density indicator and have enjoyed repeated validation of it in reefs around the equator.

(It has caused significant frowning from TSA agents looking through my suitcase as they ponder the question; “What is this thing and can it interfere with flight safety?”)

I use it routinely and prefer it to glass tools because the glass can be easily broken while the plastic is amazingly durable.

The other issue with refractometers is that they are heavy and take up space where the frags can fit for the flight home. TSA doesn’t allow calibration solutions in the carryons either.

ha ha, well the veegee doesn't ever seem to need recalibration as it is not prone to drifting so no problem there

 

[KrisReef]

ha ha, well the veegee doesn't ever seem to need recalibration as it is not prone to drifting so no problem there

When I started I used the hobby grade glass hydrometers and they are also reasonably accurate (and easy enough to make repeatable batches of water with). The really good ones are accurate and precise but I am so clumsy I can’t afford to use them. The more expensive they are the fast I find a way to break them.

 

[Fish Fan]

I very much like the Milwaukee digital refractometer. It’s super easy to use and read, seems accurate, comes with calibration fluid, and was reasonably affordable.

Milwaukee Digital Refractometer at BRS

 

[Randy Holmes-Farley]

When I tested a deep six swing arm years ago, it did a good job of correcting temp issues, but was off in absolute terms:

Chemistry and the Aquarium: Specific Gravity: Oh How Complicated!

This month, Randy explains and reviews specific gravity.

reefs.com

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.