Honestly I only recommend the Leopard Wrasse if you are patient and willing to wait for your LFS to do a bulk order on them and pick one that is active and feeding on frozen foods 2-3 weeks after it arrives in the store. They are notoriously poor shippers and by nature they are picky copepod eaters to boot, so only the more adaptable individuals last long in captive environments.
The established Tang and Flame Angel will be a real consideration for any new additions as they will likely treat any new addition in a tank that small as a threat/invader and the results will not be good. Leopard Wrasses tend to be timid when it comes to aggression and are very likely to be bullied by an assertive fish. A Melanurus Wrasse would be a better choice as they are generally more hearty and tend to have a wide variety of diets. That and they are a pretty good balance. They generally don't start fights, but they will defend themselves against more aggressive fish. I watched my Juvie Melanurus take on a new Yellow Tang and CB both at the same time when they tried to establish a new pecking order in the tank (and both exceeded the size of the wrasse at that time). Both the Yellow Tang and Coral Beauty got a surprise when they found this fish trying to bite their tails off and not backing down. They both pretty much left the wrasse alone after that and even swam together with it once they got more established. The same wrasse also put an aggressive butthead of a snowflake ocellaris clownfish in place. The Clownfish came in and tried to bully everyone in the tank. The Melanurus Wrasse took it for a bit and then it decided it had enough and spent the next couple of days beating the living crappola out of it (I even saw the wrasse grab the clownfish by the tail and shake it like a ragdoll). After that it backed off and pretty much left it alone, but it would give the occasional little reminder nip to the clown so it could remember who was boss.
