Besides salt is there anything else I need to do/add/use when owning a brackish aquarium?

There sure is. If you're trying to create a true brackish aquarium, you will need more than just salt. Oceans don't just contain salt, as I'm sure you're aware. There are a lot of trace elements floating around. Get some marine salt mix, a hydrometer, and shoot for a gravity of 1.008.. However, it depends a lot on what species of fish you're going to put in it. Just keep in mind, when you change the water, you're going to want to add water that's premixed with the proper amount of marine salt or you can severely stress your fish. Edit: No, Brackish water is not fresh water with a little bit of salt in it. That's fresh water with a little bit of salt in it. Brackish water is where fresh water and marine water mix. This is found in nature in coastal pools and where rivers and streams empty into the ocean. There is a difference.  more