Salinity too high and won’t go down

[maxmale96]

Hey All - so relatively new (4 months in) and my tanks been doing fine. A few days ago I noticed the corals all didn’t seem to be doing well (not expanding) so I did a water change with LFS reef crystal pre mixed water. Still didn’t help. I do regular water changes so never really needed a salinity measurer. I tested and noticed that my magnesium was really high at 1700 and calcium also high at 700. Did some research and saw that this could be due to salinity problems, so I bought a refractometer. Tested today and found it to be 1.038 which obviously is not good. Added a bunch of RO water and it immediately went down to 1.030 (still high). Checked a few hours later and it went up to 1.035. Did a larger water change with RO water and it went down to 1.025. Checked a few hours later and it was up to 1.030

How does it keep going up? I’ve done like a 25% water change with just RO water and it isn’t helping as much as I thought it would.

Also:
Nitrite: 0
KH: 140
Phosphate: 0.25
PH: 7.8
Nitrate: 2
Ammonia: 0
Alkalinity: 7
Calcium: 700
Magnesium: 1700

 

[Cichlid Dad]

How are you topping off your evaporation

 

[maxmale96]

How are you topping off your evaporation

I’ve been putting in salt water (which I also researched that it could have been the problem)

 

[Dipi]

If you are just adding RO water and have some sort of ATO, it will lower your salinity instantly but the excess water will stop your ATO. Them, the water will evaporate until it reaches the setpoint of you ATO, wich means all that extra RO water has evaporated and you end where you started in termos of salinity. To decrease salinity you must remove saltwater and them complete with RO

 

[Cichlid Dad]

Only fresh water evaporated and you added salt water. This is the issue

 

[maxmale96]

Only fresh water evaporated and you added salt water. This is the issue

But shouldn’t it have been fixed today when I did a largeish water change with just RO water?

 

[DrkNMighty]

Yep. You should be topping off with RO water and not salt. This will fix your problem.

 

[Cichlid Dad]

But shouldn’t it have been fixed today when I did a largeish water change with just RO water?

How are you calibrating the refractometer. What are you using for the light source for looking through the refractometer

 

[Salty_Northerner]

Water evaporates and the salt stays. Adding more SW just increases the salinity.

 

[maxmale96]

How are you calibrating the refractometer. What are you using for the light source for looking through the refractometer

Used RO to calibrate and then using my window (outside) as the light source

 

[NonstopSoda]

All you parameters are out of wack, I suggest doing a 40-50% water change and then slowly doing 5-10% every other day until parameters are back at normal levels, Also do not top off with more saltwater. water evaporates and salt does not. top off with RO water and it should stay steady.

 

[JayM]

Used RO to calibrate and then using my window (outside) as the light source

Don’t use RO to calibrate a refractometer. That just calibrates the tool to “zero”, but it may still be off significantly enough to be a problem at 35ppt/1.026sg.

 

[maxmale96]

Don’t use RO to calibrate a refractometer. That just calibrates the tool to “zero”, but it may still be off significantly enough to be a problem at 35ppt/1.026sg.

What should I use then?

 

[JayM]

You can buy calibration fluid, or make your own.

DIY Calibration fluid

 

[Cichlid Dad]

Used RO to calibrate and then using my window (outside) as the light source

Get a calibration fluid from Amazon. I don't care what anyone else says. RO water will not get you accurate results

 

[VintageReefer]

And empty any sw from your ato and replace with rodi

Ato should only have freshwater rodi.

Water evaporates and salinity increases because the salt stays behind. You need to replace with fw to correct the salinity swing.

 

[Randy Holmes-Farley Verified Community Expert]

How does it keep going up? I’ve done like a 25% water change with just RO water and it isn’t helping as much as I thought it would.

Within the specs of refractometers and your ability to estimate water volume, it is close enough.

Just always use RO/DI di for top off and everything will be fine. Since SG is still too high, just slowly remove some salt water each day and add extra RO/DI until you get to your target.