Lowering Salinity via Water Change Advice

[Hair Algae Wizard]

Folks,

My salinity is a bit high, at 36 PPT, and I would like to lower it to 35. The level has been confirmed with a freshly calibrated refractometer, and a Hanna salinity tester.

System volume is 220g, and I plan to do my usual weekly 10% water change. Can I safely lower the salinity by lowering the water change salinity, or should I consider a different method? The tank currently only has inverts in it. Also, if doing the water change at a lower level is safe, what should the target be? Is there a calculator or formula I can reference?

Thanks!

 

[Crabs McJones]

I would just continue to do your water changes as normal with the water change water at the salinity you want. It'll come down slowly 36 PPT won't hurt anything

 

[Hair Algae Wizard]

I would just continue to do your water changes as normal with the water change water at the salinity you want. It'll come down slowly 36 PPT won't hurt anything

Thanks!

 

[Jimmyneptune]

Could you just take out a few gallons of water daily and replace with RODI until you reach desired salinity?

 

[AllSignsPointToFish]

I've done this on more than one occasion. Your salinity difference is the same difference I've had to correct for. My 125 gallon system salinity will creep up to 36 ppt (SG 1.027) from the normal 35 ppt (SG 1.026). I use a weighted average calculation and then mix up my water change water with the lower salinity. Works every time like a charm, and the corals have never noticed.

If you're interested, here's how the calculation goes.
220 gallon system volume
22 gallon water change (10%)
220 - 22 = 198 gallon water will not be changed
Starting salinity 36 ppt
Desired salinity 35 ppt
x salinity of water change needed for the correction

198(36)+22(x)=220(35)
Solve for x, and x = 26 ppt.

So, you will need 22 gallons at 26 ppt salinity. Since the water change volume is pretty small, the salinity needs to be quite a bit lower to compensate for the large volume of water remaining in the tank. If you just add the water to the system slowly over the course of a couple of hours to avoid potential areas with low salinity (allow for mixing), the system salinity will be where you want it and the residents won't even notice.

If you do a larger water change volume, then the salinity difference will be smaller and even less noticeable.

 

[Hair Algae Wizard]

I've done this on more than one occasion. Your salinity difference is the same difference I've had to correct for. My 125 gallon system salinity will creep up to 36 ppt (SG 1.027) from the normal 35 ppt (SG 1.026). I use a weighted average calculation and then mix up my water change water with the lower salinity. Works every time like a charm, and the corals have never noticed.

If you're interested, here's how the calculation goes.
220 gallon system volume
22 gallon water change (10%)
220 - 22 = 198 gallon water will not be changed
Starting salinity 36 ppt
Desired salinity 35 ppt
x salinity of water change needed for the correction

198(36)+22(x)=220(35)
Solve for x, and x = 26 ppt.

So, you will need 22 gallons at 26 ppt salinity. Since the water change volume is pretty small, the salinity needs to be quite a bit lower to compensate for the large volume of water remaining in the tank. If you just add the water to the system slowly over the course of a couple of hours to avoid potential areas with low salinity (allow for mixing), the system salinity will be where you want it and the residents won't even notice.

If you do a larger water change volume, then the salinity difference will be smaller and even less noticeable.

Excellent. Thank you as well!