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Old 05-19-2017, 09:14 PM
Mr. Miyagi's Avatar
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Real Name: Bret
Default Salinity water change formula

So I am not sure if anyone has ever sat down and figured out a formula to slightly increase or decrease your salinity but I did so I figured I would share. It is:

[(Desired gravity * total system gallons) - (system gallons after taking water out for water change * current gravity)] / gallons of water change = water change gravity


I have 1.024 salinity in my system and I want 1.025 and I have 225 gallons in my system. I do a 20 gallon water change so the math is:


Hope this helps!
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Old 05-19-2017, 09:29 PM
Mr. Miyagi's Avatar
Mr. Miyagi's Tank Specs
Join Date: Dec 2016
Location: Swartz Creek
Posts: 28
Zip Code: 48473
Real Name: Bret

And before everyone goes crazy about calcium, KH, etc I use a few different salts for what I'm trying to fix (normally adjust my salinity back to 1.025 every 3-6 months if it gets off) I use a lower KH salt when adjusting salinity so I don't burn my sps unless I need to bring KH or ph up then I use a salt like reef crystals when doing it. Again advanced topics so I would hope you guys see the big picture.
Old 06-18-2017, 11:34 AM
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Join Date: Nov 2004
Location: Dewitt MI
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Default More formulas

Here are a series of formulas. They work with PPT, not sure about SG.

TV= Tank Volume
C= Change amount TV*(ES-SS)/(CS-SS)
SS= starting salinity
ES= ending salinity +(((TV-CA)*SS)+(CS*CA))/2
CS= Salinity of water change +((TV*ES)-(TV-CA)*SS)/CA
I have them set up in an excel spreadsheet and just enter the known data.


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