Salinty calculation

[seansod]

I am setting up a 90 gallon reef tank and checked my salinty after 3 days and it is only 1.014. What I am trying to figure out is how much salt to add to raise it to 1.025. I know there has to be an easy equation to figure it out. Right now the salt says 1/2 cup per gallon so if I have 110 gallons at 1.014 how much salt needs to be added to raise to 1.025 or so.

Thanks Tony

 

[Randy Holmes-Farley]

You need to add a bit less than half (44%) of what it takes to go from fresh water to a sg of 1.025.

So assuming your 1/2 cup per gallon is roughly right, then add about 1/2 x 90 x 0.44 = 20 cups. However, the total water volume may be less than 90 gallons if the tank has rock and other stuff in it.