Making Brackish water for a 120g tank

[Rafini]

Hey I made a thread in General but it got moved to general salt, and nobody seems to comprehend the Idea of making Brackish water and think I am talking about topping up an existing marine aquarium.
I have a fully freshwater 120g tank with two archers in it, I want to increase to .002 SG. The salt I am using (instant ocean) says to use 1/2 a cup per US gallon for full strength Sea water.

So can anyone help me out calculating how much salt I need to mix to increase my SG to .002?

Thanks ! Rafini

 

[robert.mccook.elm]

i suppose that would depend on what instant ocean considers saltwater. if 1/2 cup per gallon give you 1.020, which is low end saltwater, then 1/4 cup should give you 1.010, and 1/8 cup should give you 1.005, and 1/16 cup should give you 1.0025 or so. so in theory that would be 1 tablespoon per gallon. but from what i know about making brackish water is that you just have to slowly add is and keep checking your salinity level. hope this helps.