Right Amount of Salt Mix for Hypo?!?!?

[FxdupCobra]

I know this is a silly question but has anyone figured this out.
I am trying to calculate, if I wanted to do hypo in order to have already made salt water for water changes what is the right amount of salt to be added.

So if 2.5 cups of salt = 1.023(in a 5 Gallon container)
Then does that mean 2.46 cups of salt = 1.009 ?????

I dont want to keep guessing and having to add salt and ro/di everytime I am off?

 

[kevin2000]

Perhaps the easy way to think of hypo water is that it has approximately 1/3'rd the salinity of std reef water. Many people just mix up there std reef water and add two part FW to get them darn close to the 1.009.

When I start a hypo Qt and only have one small fish I just fill my ten gallon tank with 1/3 normal salinity water - add the fish - and then drip RO water until the tanks almost filled (then fine tune) .. pretty simple but won't work if you have a large fish or multiple fish.