Butterfly Fish Species
There are over 100 species of fish that are included in the Butterfly fishes but many are not recommended for the home saltwater aquarium for a few different reasons. Some of the butterfly fish in this family are known "corallivores" which means they will eat coral polyps. This food source can be difficult and expensive to reproduce in most home aquariums. They don't handle shipping very well either. Slow acclimation and quarantine is recommended before introducing into a display fish tank with other fishes.
The Butterflys are usually found in shallower waters off the coast where there is high water movement, slightly warmer water temperatures and lots of places for them to hide. It can be a good idea to try and recreate this in your aquarium. Use some power heads to create more water movement, which should increase the amount of oxygen in the water and make it a little warmer from the heat produced by the submerged power heads.
Some are worse than others when it comes to survivability in the aquarium with many species being on the "hard to keep" list. Research the butterfly species you're interested in before bringing it home from the store. Ask the fish store to hold it for a week or so and ask them to feed it before you buy it. If they don't want to hold it for you, offer to make a deposit, it may change their mind.
Copperband Butterfly Fish
Even though you may read that these are one of the better choices for butterfly fish, it's been our experience that the Copperband can still be tough to keep. They can be quite finicky with normal aquarium foods but do a nice job on aiptasia.
This is one of the largest of the butterfly fish. They can get up to 12 inches and need the largest of aquariums. They can also be difficult to acclimate and feed.
Sometimes referred to as the "Poor Man's Moorish Idol" because they do look quite similar. They are way easier to keep than the Moorish Idol.
Raccoon Butterfly Fish
The Raccoon Butterflies can reach about 8 inches (20 cm) or so and have a pretty good track record amongst hobbyists as being relatively (for Butterfly fish) to keep.