Until I get all my live rock for my tank, which is actually a 5.5 g, not a 6 like I though, I want to run a HOB filter. Its an old one from a FW tank, would that be okay, and what type of media should I use?
That's fine if you run that HOB filter. I would use just use carbon or any other form of media to remove excess hazardess chemicals from the water already in the tank.