mudskipper newbie

Hi- Just joined. I've been fascinated with mudskippers for years, and was very suprised to see them in a pet store in Boston last week. I didn't know I could see them outside the New England aquarium. I bought 3, and was told to keep them in fresh water and feed them bloodworms. Then I started the research, and see web postings saying that I must create brackish water, use a large aquarium, feed live food, and keep the water warm. I have a four foot aquarium in the garage that I could set up, but I don't really know how to make brackish water and can't be sure how much of this advice I need to heed. Any advice from experienced skipper-keepers?