How to safely lower salinity in 850 gallon reef system

[14 foot reef]

Could use some detailed help on safely lower my salinity. My system is accurately measuring salinity at 1.028 or 37 PPT want to lower to 1.025 or 35 PPT.
Obviously I'm pulling out salt water and topping back off with fresh clean RODI, the question is, at what rate can I do this, and should I buffer the RODI in order to NOT affect my DKH?

And a side note, would this level of salinity have a negative affect on my SPS, I've lost a few and color is not good at all. Triton test came back fairly good minus a few small things.
Am = 0
Nitrite = 0
NitRATE = 12-16
PH = 8.26
DKH = 7.7
Ca = 450
Po4 = .03
Mg = 1600

Thanks in advance for any advise.

 

[Randy Holmes-Farley Verified Community Expert]

FWIW, the specific gravity of 35 ppt seawater is about 1.0264, so you do not have that far to go if 35 ppt is the goal.

The salinity you have not is not a problem for corals, but if you remove 1% of the tank volume each day (and replace with fresh water), the sg will go like this (by day):

1.0277
1.0274
1.0272
1.0269
1.0266
1.0264

 

[14 foot reef]

Randy, thanks. just realized my goal I put was incorrect. My true goal would be 33 ppt 0r 1.0249. Would your formula for correction still be 1% max per day until down to my 33 ppt goal?
Also should I buffer the RODI top off ? or is straight RODI ok to replace with?

 

[Randy Holmes-Farley Verified Community Expert]

Randy, thanks. just realized my goal I put was incorrect. My true goal would be 33 ppt 0r 1.0249. Would your formula for correction still be 1% max per day until down to my 33 ppt goal?
Also should I buffer the RODI top off ? or is straight RODI ok to replace with?

1% daily seems like a nice, conservative approach, and limits your work on a given day since it's a lot of water.

I wouldn't add anything to the RO/Di.

 

[don_chuwish]

I've found this helpful in the past:
https://www.hamzasreef.com/Contents/Calculators/DirectSaltCalculator.php

 

[14 foot reef]

I've found this helpful in the past:
https://www.hamzasreef.com/Contents/Calculators/DirectSaltCalculator.php

need to lower, not raise. that calculator doesn't allow figuring lowering salinity

 

[vegamedic]

need to lower, not raise. that calculator doesn't allow figuring lowering salinity

https://www.hamzasreef.com/Contents/Calculators/TargetSalinity.php

https://www.hamzasreef.com/Contents/Calculators/ResultingSalinity.php

There's quite a few salinity calculators on the same site don linked. the above 2 should get you where you need

 

[14 foot reef]

That works perfect.......
100 gallons of 1.028 out at a rate 0f 10 gallons a day for 10 days will get me too 1.025 after 10 days.

Thank you