Dropping salinity

[Nem0]

Hey guys, when I started cycling my tank (about 1.5 weeks ago) I had a consistent salinity of 1.023. I measured today and the salinity dropped to around 1.020. Is this normal? I'm going to bring it up to about 1.025 but I am just curious. The overall water level has dropped, by just a bit, but I would have expected my salinity to increase not decrease with the evaporation of fresh water

Furthermore, I have calibration fluid for my refractometer. The first time I measured I adjusted it and put it at 35ppm. I relooked at it/recalibrated it today and when I put the calibration solution it was at 40ppm. Not sure if any others are experiencing variations with their calibration/have tips!

 

[Dom]

Are you using auto top off? If so, you may be adding water at a rate which is greater than water evaporates. If this is the case, your concentration of salt will be reduced causing a drop in salinity.

Remember: only water evaporates. Salt doesn't.

 

[Captain Quint]

Are you using a skimmer?

Tank size?

 

[Nem0]

@Dom nope, I haven't topped off the tank/added any water. the level decreased by just a little but, not anything significant

@Captain Quint I do not run a skimmer, its aa 9gallon fluval flex

 

[André Brasil]

No insight to share...but I'm also curious about this as i sometimes feel this happens in my system as well!

 

[Mastiffsrule]

You are 100% correct. If your water evaporates it will concentrate your water and raise the salinity. My best guess may be slight variance when reading and calibrating. I may suggest calibrate it once and make sure your salinity is right. Leave the refractor calibrated as is and check again for a few days. Chance are you should see consistent results except for minor changes from evaporations or topping off.

Refractors can be sensitive. I usually calibrate once, handle carefully and calibrate every so often.

And I know I’m going to get flack on this but I still use hydrometers as back up.

 

[RJinPV]

The only way for salinity to drop is to remove saltwater and replace it with freshwater. Be sure to check for leaks. If you aren't removing saltwater via a wet skimmer then it's going somewhere..... If you really haven't added any water then the measuring technique would have to be inconsistent (comparing uncalibrated refractometer readings with calibrated readings)

 

[Nokiaec11]

If you have leaks at spots in the plumbing you will notice salt build-up in those areas, or if you has some splashing in you sump you see salt around the sump area and that coul account for actual salinity decrease, but even that would be very minimal...I agree with the refracto comments