Commonly referred to as Butterfly Fish, are an often overlooked family of fish that is quite a diverse family. There are many species of butterflyfish, with quite different requirements and behaviours (including diet). Some of the planktivores and generalists do well in captivity, but most species are difficult to maintain, and obligate corallivores nearly impossible .
Suitable Species for Reef Tanks
Some butterflys can be successfully maintained in reef tanks while posing little threat to corals. Others share a similar risk profile to dwarf angels or Centropyge sp.
Long term success with these fish is influenced by many factors including food availability, order of introduction, system size, individual temperaments and suitable tankmates. Quarantine is also beneficial to manage diseases on new specimens and adjustment to captivity. The major problem is whether a system is suited to these fairly passive fish. Most will not tolerate aggression and may go on a hunger strike and ultimately waste away if kept with unsuitable tankmates.
Forcipiger flavissimus (Long Nose Butterfly) is among the safest of the species, seldom posing a threat to any corals, though possibly to some invertebrates. Equally safe are the true planktivores such as Hemitaurichthys polylepis (Pyramid Butterfly). Posing a little more risk are Chelmon rostratus and C. marginalis (Banded Butterflys). These are all affordable and regularly available.
Finally, the deepwater butterflys from the Roaops complex are a little more tricky and can be likened to pygmy angels. Though largely planktivores, they may nip periodically at meaty corals. They are also somewhat harder to find and include the very personable Chaetodon tinkeri after whom the complex was originally named.
Small, colourful, disclike fishes with small protractile mouths with small brush like teeth., continuous dorsal fins, body and head covered with small scales extending onto the median fins, and rounded to emarginate tails. Most species are diurnal and rest amount corals or rocks during the night. Diet differs greatly amoung the species. Many feed on a variety of cnidarian polyps or tentacles, small invertebrates, fish eggs and filamentous algae. Others are specialists with some feeding exclusively on coral polyps. Coral polyp feeders tend to be highly territorial around the areas of their food source. Most species patrol a home range. Some species are planktivores that aggregate in large schools high in the water and may range into deep water. Many speices occur as heterosexual pairs that may remain together for years, if not life. Larval stage is lengthy, from a few weeks to perhaps 2 months, and with distinctive late tholichthys stage in which head and front of body are coverd in bony plates. 
There are currently 114 described species found in 10 genera belonging to the family Chaetodontidae. Chaetodon has the largest number of species.
- Chaetodon kleinii - Klein's Butterflyfish
- Chelmon rostratus - Copperband Butterflyfish
- Forcipiger flavissimus - Yellow Longnose
Common Imported Species
- Chaetodon burgessi - Burgess' butterflyfish
- Chaetodon collare - Redtail butterflyfish
- Chaetodon falcula - Blackwedged butterflyfish
- Chaetodon mesoleucos - White-face butterflyfish
- Chaetodon mitratus - Indian butterflyfish
- Chaetodon quadrimaculatus - Fourspot butterflyfish
- Chaetodon semilarvatus - Bluecheek butterflyfish
- Chaetodon tinkeri - Hawaiian butterflyfish
- Chaetodon triangulum - Triangle butterflyfish
- Chaetodon xanthurus - Pearlscale butterflyfish
- Reef Safe Butterflyfishes? by Matt Wandell - Reefs Magazine
- Family Information - FishBase
- Fish Identification: Find Species - FishBase
- .,(Lieske Myers 1996): Lieske, E., Myers, R., Coral reef fishes : Caribbean, Indian Ocean, and Pacific Ocean : including the Red Sea, Princeton University Press: Princeton, 1996.
- (http://www.manhattanreefs.com/forum/reefs-magazine/78104-reef-safe-butterflyfishes-matt-wandell.html): Wandell, M., Reef Safe Butterflyfishes?, Reefs Magazine, 2010.