How Many Fish Can You Put In A Saltwater Aquarium?

It's a super common beginner question:

"How many fish can I put in my saltwater tank?" Of course there is no simple answer, so instead of giving you ifs, buts, and maybes, we are just going to answer the question.

Five different tank sizes ranging from 15-150 gallon beauties, with a simple, concrete answer for each. For example. How many fish can you put in a 15 gallon cube? 3 Fish.