salinity

[parrotchute]

So, I'm prepping for the water change (after 6 weeks away); my girlfriend had done 2 water changes while I was gone, but was using the refractometer with good salinity readings...
the last time she did it, she thought the salinity was low.

When I checked it today, it was 1.020, down from .026 from when I left. Could the salinity have dropped this much with normal water changes, or is it likely the refractometer is out of calibration? I've never calibrated it after the first time, maybe I should do it again? Is it easy for them to go out of calibration? I figured it was purely mechanical and would stay normal.

Temps have been constant..

Alex

 

[yote]

At least check the calibration on it.Its possible that it did get out of whack.
Then just do your water change like normal and top off with saltwater mixed to 1.026 untill the tank waters back where its supposed to be.

 

[ndepratt]

well if you don't mix the water properly, and let it sit and mix long enough.... then you can get poor readings, for example the water on top being saltier than on the bottom.

so it could be she didn't mix long enough, thought she had it done properly, and used that when it was actually low.

it happens... test someone's water that you know is a constant salinity, or you can get a rough estimate by mixing a new batch using half a cup (i believe) per gallon of water, and it should be roughly 1.025.

 

[dcantucson]

Use some RODI water and check the calibration. Should read ZERO if it's calibrated correctly.

 

[ccCapt]

Use some RODI water and check the calibration. Should read ZERO if it's calibrated correctly.

That is a good way to see if your refracto reads 0 correctly, but doesn't really tell if it's calibrated correctly to 35 ppt (1.026 SG). Get a bottle of Pinpoint salinity calibration fluid. It's a standard solution which will read exactly 35 ppt (1.026 SG) if the refracto is properly calibrated.

 

[Hornet]

If you have the refractometer with the adjustment screw maybe you or your girlfriend accidentally knocked it out of whack. If you don't have the calibration fluid just use some ro/di and calibrate it to 0. But you should still consider getting a bottle of the 53.0 mS fluid like ccCapt recommends. One small bottle will last you for a long time.

 

[parrotchute]

If you have the refractometer with the adjustment screw maybe you or your girlfriend accidentally knocked it out of whack. If you don't have the calibration fluid just use some ro/di and calibrate it to 0. But you should still consider getting a bottle of the 53.0 mS fluid like ccCapt recommends. One small bottle will last you for a long time.

Thanks for the advice guys; I took the refracto to the lsf and it calibrated a-ok...
Looks like my salinity has dropped, going to bring it up slowly in the next change...