Freshwater Dip Instead Of Qt.

[FLcracker94]

Ok, I have a 12ga (US) Biocube, and I'm getting a 75 ga (US) tank. When I get the 75, I'm giving the 12 to my grandma for FW. I'm giving it to her because I don't like QT's, because once you have your fish, you dont usually use it. I've heard that you can to a FW dip. I was wondering how you do this.

Basics:
How do I set it up
Is it accually FW or SW
How long do they stay in it