Help on salinity...

[revenant]

I have a couple hydrometers which show erratic readings... and a floating glass one which I want to trust more... how do I get an accurate salinity reading?!?

According to the glass I am 1.020... but the plastic point of sale ones way higher... what to do??

 

[ReQuackulous]

You can try a refractometer? They typically have a knob to calibrate on RODI water and then you can let it rip. Additionally local fish stores may validate your readings. Refractometers are pretty cheap and easier to read.

 

[revenant]

You can try a refractometer? They typically have a knob to calibrate on RODI water and then you can let it rip. Additionally local fish stores may validate your readings. Refractometers are pretty cheap and easier to read.

Never used one but guess I have to get one.

 

[Nick428]

RO water should be 1.000 so if that measures out correct it should be accurate. Also you need to find out what temperature they were calibrated for the instant ocean one is 68F. A simple hidden air bubble could be lifting the hydrometer.

 

[Crabs McJones]

You can try a refractometer? They typically have a knob to calibrate on RODI water and then you can let it rip. Additionally local fish stores may validate your readings. Refractometers are pretty cheap and easier to read.

I agree, the swing arm hydrometer can have a couple variables for inaccurate readings such as micro bubbles on the swing arm causing it to show an higher reading then what it actually is. A refractometer and a bottle of calibration solution will get you an accurate reading

 

[revenant]

I agree, the swing arm hydrometer can have a couple variables for inaccurate readings such as micro bubbles on the swing arm causing it to show an higher reading then what it actually is. A refractometer and a bottle of calibration solution will get you an accurate reading

Yeah seems right.. wow.. didn’t know these would be so off though.. garbage and waste of money basically.. the glass reader is hard because I have so much flow in my tank and sump.. but I can compare the differences from my mixing barrel to get a gauge on this.. now to get a refractometer... I had a pinpoint digital meter 10 years ago but it needed a lot of calibration... still thinking about getting another ...

 

[revenant]

RO water should be 1.000 so if that measures out correct it should be accurate. Also you need to find out what temperature they were calibrated for the instant ocean one is 68F. A simple hidden air bubble could be lifting the hydrometer.

My RO is 0.00 on the TDS meter.. got it.. yeah the temp and small air bubbles.. need to get meters that are not distracted by that..

 

[Nick428]

My RO is 0.00 on the TDS meter.. got it.. yeah the temp and small air bubbles.. need to get meters that are not distracted by that..

Oh i ment on the hydrometer RO water is 1.000 SG. if the hydrometers off it will be below or above 1.000 with RO water and should be 68F.

 

[revenant]

Ordered
4.6 out of 5 stars 911 Reviews
Salinity Refractometer for Seawater and Marine Fishkeeping Aquarium 0-100 PPT with Automatic Temperature Compensation... 20 bucks.

 

[revenant]

Oh i ment on the hydrometer RO water is 1.000 SG. if the hydrometers off it will be below or above 1.000 with RO water and should be 68F.

Baseline.. got it.. thanks!!

 

[revenant]

Thanks everyone!!

 

[Opus]

Yeah seems right.. wow.. didn’t know these would be so off though.. garbage and waste of money basically.. the glass reader is hard because I have so much flow in my tank and sump.. but I can compare the differences from my mixing barrel to get a gauge on this.. now to get a refractometer... I had a pinpoint digital meter 10 years ago but it needed a lot of calibration... still thinking about getting another ...

You should turn your pumps off in your tank if you are trying to get a reading in there with the glass one. It should be really accurate. They are usually calibrated at 77f I believe.

Personally I've gone digital and I don't think I can go back to a regular refractometer. I found them to hard to read for my eyesight. I have the Hanna hand held and the milwaukee digital and love them.

 

[Randy Holmes-Farley Verified Community Expert]

Check carefully for the reference temperature printed on the floating glass hydrometer. They vary.

once you know that and the temp of the water, you can correct it using a calculator or table like this:

Hydrometer Temperature Correction Calculator

Measuring gravity with a hydrometer can be affected by temperature, so we recommend using this hydrometer temperature correction calculator to make sure you're recording your gravity accurately! I frequently find myself taking multiple gravity readings during the brew day and at various stages...

homebrewsupply.com

The swing arm type corrects for temp automatically.

 

[Brew12]

Ordered
4.6 out of 5 stars 911 Reviews
Salinity Refractometer for Seawater and Marine Fishkeeping Aquarium 0-100 PPT with Automatic Temperature Compensation... 20 bucks.

If it didn't come with a reference calibration solution, make sure you get one!

 

[Reef.]

Baseline.. got it.. thanks!!

Refractometers have their issues too, always check the calibration each time you use it, with a bottle of 35ppt calibration fluid, if it is staying stable you have a good one, you can then test the calibration less often.
Also clean the glass of the refractometer each time you use it and dry the glass, the tiniest residue of water on the glass will give you an incorrect reading, also I was using a pipette to drop the water on the glass, again this lead to incorrect results as the inside of the pipette had salt residue, i now use a spoon I have rinsed in RO water and dried, I also do 2/3 tests at a time just to check I’m getting a consistent result.

 

[nereefpat]

The floating glass hydrometer is more accurate than both a swing arm hydrometer and the refractometer, and it never needs calibration.

To measure your tank with the floating glass hydrometer, get a plastic graduated cylinder from amazon. Put the tank water in it, then drop the hydrometer in a give it a spin. You will need to find out what temp the floating glass hydrometer is designed for, then use the chart that Randy posted.

 

[revenant]

The floating glass hydrometer is more accurate than both a swing arm hydrometer and the refractometer, and it never needs calibration.

To measure your tank with the floating glass hydrometer, get a plastic graduated cylinder from amazon. Put the tank water in it, then drop the hydrometer in a give it a spin. You will need to find out what temp the floating glass hydrometer is designed for, then use the chart that Randy posted.

ok I will get a plastic graduated cylinder from amazon. Thanks!

 

[vetteguy53081]

Buy one you cant afford and get the best results. False salinity has gotten the best of me more than once !

Refractometer:

Digital tester:

 

[Daniel92481]

Buy the Hanna digital salinity/temp checker as mentioned above, and never look back.

 

[revenant]

Going to at least start with the cylinder and floating glass hydrometer... it will never give you an off reading.. the salt in the water will push it out to the right level each time.. depending on temperature too..