Refractometer Question

[NorCalReefing]

I’ve got 3 separate tools to measure salinity. A Red Sea refractometer that I keep having to calibrate, and 2 different swing arms that I’ve had forever.

I recently went ahead and recalibrated the Red Sea with some solution I purchased on Amazon (continuum reagents at 1.026). Unfortunately, my tank now keeps measuring around 1.029/30 using the Red Sea… the swing arms have read between 1.023/24. So here’s my question, what should I trust?

Also, does anyone else seem to have issues with their RedSea refractometer? Seems like it’s constantly needing to be recalibrated.

 

[Randy Holmes-Farley Verified Community Expert]

I’ve got 3 separate tools to measure salinity. A Red Sea refractometer that I keep having to calibrate, and 2 different swing arms that I’ve had forever.

I recently went ahead and recalibrated the Red Sea with some solution I purchased on Amazon (continuum reagents at 1.026). Unfortunately, my tank now keeps measuring around 1.029/30 using the Red Sea… the swing arms have read between 1.023/24. So here’s my question, what should I trust?

Also, does anyone else seem to have issues with their RedSea refractometer? Seems like it’s constantly needing to be recalibrated.

You can test all of them in diy fluids:

Reef Aquarium Salinity: DIY Calibration Standards

Reef Aquarium Salinity: DIY Calibration Standards By Randy Holmes-Farley One of the most important issues facing marine aquarists is providing a suitable environment for their aquaria's inhabitants. Among the important properties for a marine...

www.reef2reef.com

 

[Seansea]

I have the same problem. I have the hanna salinity checker, swing arm and a kactoily. All say some thing different. With icp tests I have determined the hanna is .002 high swing arm is .001 high and kactoily is all over the place. Use icp to nail ot and figure out where yours sit

 

[NorCalReefing]

You can test all of them in diy fluids:

Reef Aquarium Salinity: DIY Calibration Standards

Reef Aquarium Salinity: DIY Calibration Standards By Randy Holmes-Farley One of the most important issues facing marine aquarists is providing a suitable environment for their aquaria's inhabitants. Among the important properties for a marine...

www.reef2reef.com

Thanks Randy, this was very helpful! I made the solution with a teaspoon of salt and 161mL of water. It matched the calibration solution I purchased using the RedSea. My swing arm is measuring at 1.022.

Unfortunately, that means my tank is currently measuring around 1.028/29 at the moment. Going to slowly get it down to 1.026.

The good news is, everything is still looking good and no corals or fish are showing any issues at the higher salinity.

The Red Sea Refractometer appears to be accurate but seems to require calibration often.

 

[Ef4life]

I gave up on refractometers and went to a glass hydrometer. They are very delicate so they might not be for everyone.

High Precision Hydrometer

Ensure that your equipment is reading correctly and your aquarium is at the right salinity with Tropic Marin's High Precision Hydrometer. Many tank inhabitants are sensitive even to minor changes of the water conditions. Unfortunately as we've all experienced, salinity reading equipment as...

www.bulkreefsupply.com

 

[Thumbster]

I used this scale and Randy’s formula to make my own standard about six months ago.
It makes about 3.5 ounces of fluid and I have it in a little dropper bottle that I pull out every now and then to double check my refractometer. I still have 95% of it left. It lasts a loooong time.

Side note: I took the 100g weight that came with the scale to the state department of weights and measures to see how accurate it was and it was within .006g of being exactly 100g. Im sure each weight is slightly different but I just happened to be going there so I took it with me.