Are you serious about a clownfish in a 1 gallon? Please tell me your kidding. If not you can PM me for some advise or post in the saltwater section.
Heater? Yes, salt? Yes... Premixed. You need to know the basics before you start anything.
"When creating an aqua scape, strive for the beauty of imperfection, as its art and there is no wrong or right, it's left open for interpretation" James Findley