I got my first job at 13 working in a fish store (same as you I had never dealt with saltwater tanks till I worked there). I worked in fish stores until I was 17, by the time I left the fish store to go to college I had a 209g Saltwater tank, 120g saltwater tank, 2 55g (1 brackish 1 saltwater) and a couple various 20g). When I started when I was 13 I had a 20g Goldfish tank (I soon learned bad idea!) and a 10g tropical tank. Fish store jobs are addicting and tend to add new different tanks to your house ! Good luck and have fun!