Whats a good match for my puffer?

my green spotted puffer is in a 20 gallon tank with a black molly, a swordtail fish, a algae sucker, a blue ram, and a neon tetra. they all seem to get along great. but as i know i have to get a bigger 30-40 gallon salt water tank for my puffer and my black molly. now when i get this tank which is going to be soon this week i wanted to know a few fish names that might get along with the green spotted puffer since he can get along with these other 5 fish.thanks for help!