Can I get some help with my salinity issues with new salt water?

[cybrook1421]

I have a brute can that holds 26 gallons of water. When I mix new salt water I put in all the RODI needed, then about half the salt I think it will need. This is all done without heaters (about 68F). I let it mix for at least 1 hour then put in the other half of the salt (minus a little). Let it mix for another hour. Then I test the salinity and make adjustments.

I have been having some trouble making sure my salinity is correct. I have a milwaukee digital refractometer (black and green one) that I have calibrated with RODI water at the same temp as the new saltwater (both bins sit right next to eachother). I am assuming that because the refractometer has auto temp correction, that I don't need to heat up my water to test it as long as I calibrate with the same temp of water.

I just did a check today using the calibration fluid that was sent with it and the refractometer is reading 1.027 instead of 1.025. The calibration fluid was also the same temp in that same room. Not sure why this is happening.

Any help or advice on how I can fix these issues or change my process would be much appreciated. I don't want to have to heat the bin of new saltwater, but I can if needed.

 

[scotty333]

Can’t answer your question unfortunately but I’m curious , are you putting fresh salt water in without matching the temp to your tank?
How big a wc?

 

[Randy Holmes-Farley]

I have a brute can that holds 26 gallons of water. When I mix new salt water I put in all the RODI needed, then about half the salt I think it will need. This is all done without heaters (about 68F). I let it mix for at least 1 hour then put in the other half of the salt (minus a little). Let it mix for another hour. Then I test the salinity and make adjustments.

I have been having some trouble making sure my salinity is correct. I have a milwaukee digital refractometer (black and green one) that I have calibrated with RODI water at the same temp as the new saltwater (both bins sit right next to eachother). I am assuming that because the refractometer has auto temp correction, that I don't need to heat up my water to test it as long as I calibrate with the same temp of water.

I just did a check today using the calibration fluid that was sent with it and the refractometer is reading 1.027 instead of 1.025. The calibration fluid was also the same temp in that same room. Not sure why this is happening.

Any help or advice on how I can fix these issues or change my process would be much appreciated. I don't want to have to heat the bin of new saltwater, but I can if needed.

What exactly does the standard say on it?

The Milwaukee only claims +/- 0.002 in sg accuracy.

 

[cybrook1421]

Can’t answer your question unfortunately but I’m curious , are you putting fresh salt water in without matching the temp to your tank?
How big a wc?

I have any auto-water change system and only changing about 1-1.5 gallons over 8 or so hours so the temp doesn't matter.

 

[cybrook1421]

What exactly does the standard say on it?

The Milwaukee only claims +/- 0.002 in sg accuracy.

Here is a picture of the bottle

 

[Randy Holmes-Farley]

Your issue seems exactly reproduced by many others in the past. I suspect poor fluid.

Milwaukee refractometer

I need advice. I purchased a refractometer and I have been using the steam distilled water to zero the unit and then when I test it against the naslow calibration solution it comes up at 1.027. When I test it against rodi water it comes out to 1.00 s.g. Should I assume that the calibration...

www.reef2reef.com

 

[Garf]

What's the "suspended dissolved salts will settle and or separate" about? I don't think that should happen, anyhow.

 

[SaltySqueeble]

You could try weighing your salt and you will be much closer to where you want to be, rather than half and some of the other half later

 

[scotty333]

You could try weighing your salt and you will be much closer to where you want to be, rather than half and some of the other half later

Yeah 1kg =30 ltrs at 1.025

 

[Randy Holmes-Farley]

What's the "suspended dissolved salts will settle and or separate" about? I don't think that should happen, anyhow.

Right. The term suspended dissolved salts seems an oxymoron. Dissolved salts are not normally considered suspended and dissolved salts will never settle out unless they become undissolved solids.

 

[VintageReefer]

That fluid is junk I don’t use it anymore. Just calibrate to zero with distilled water, then put sample on, wait 30 sec and take a reading

 

[ReneReef]

I am assuming that because the refractometer has auto temp correction, that I don't need to heat up my water to test it as long as I calibrate with the same temp of water.

The temperature of the sample water doesn't matter at all in case of an refractometer.
It's an often heard and understandable misunderstanding.

The tiny water sample practically immediately takes on the temperature of the refractometer.
The ATC serves to compensate for temperature changes of the device itself because of changes in ambient temperature. You're measuring at room temp, not at the temperature of your tank, RO water or mixing bin.

The ATC is far from instant, not very smooth, adds inaccuracy and makes the device loose its calibration fast. Generally it's best to avoid having the ATC operating as much as possible.

Do you store, calibrate and measure with the refractometer in the same room?
If not and the device is exposed to changes in ambient temperature just before calibrating and measuring that may explain some of your struggles.

P.S. the above does not apply to electronic salinity probes that you dip into the water your testing. In that case the probe takes on the temperature of the water.

 

[cybrook1421]

You could try weighing your salt and you will be much closer to where you want to be, rather than half and some of the other half later

I like doing half and half because it tends to mix better and produces less "gunk" in the bin over time. I guess I could weight and then just put in half though.

That fluid is junk I don’t use it anymore. Just calibrate to zero with distilled water, then put sample on, wait 30 sec and take a reading

I will just do that I guess. I calibrate it regularly but not all the time. I'll try waiting those 30 seconds and maybe get a backup refractometer.

Thanks everyone!

 

[cybrook1421]

The temperature of the sample water doesn't matter at all in case of an refractometer.
It's an often heard and understandable misunderstanding.

The tiny water sample practically immediately takes on the temperature of the refractometer.
The ATC serves to compensate for temperature changes of the device itself because of changes in ambient temperature. You're measuring at room temp, not at the temperature of your tank, RO water or mixing bin.

The ATC is far from instant, not very smooth, adds inaccuracy and makes the device loose its calibration fast. Generally it's best to avoid having the ATC operating as much as possible.

Do you store, calibrate and measure with the refractometer in the same room?
If not and the device is exposed to changes in ambient temperature just before calibrating and measuring that may explain some of your struggles.

P.S. the above does not apply to electronic salinity probes that you dip into the water your testing. In that case the probe takes on the temperature of the water.

Thanks for this! All of my things are in the same room, so no worries about changing environment.