IF you already have 2 clowns in a 14g I would say you are maxed out on bio-load. The recommendation is one inch of adult fish per 5 gallons of water. Depending on the clowns the adult size can be anywhere from 2 inches up and that is all the space you have. Corals and shrimp don't count against your bio-load so you are good there.
After having a sixline in my previous lightly stocked 30 gallon, I never want one again (especially in a nano). It got really aggressive as it got larger, until I got rid of it when I broke down the tank.