keiko

Hi every one!!, i usually have fresh water tank for more than 20 years and i swich my aquarium in saltwater thank, first of all i know is very diferent than freshwater, then i have to do some stuff every week. But my questions are, can somebody help me how do i know when the bacteriological cicle is done?, how i know that? (i all ready set up the aquarium a week ago), second, if i can add a fish right now, what is the perfect one to beggin and how do i post to introduce into the aquarium?