The False Double Saddle Butterfly (Chaetodon ulietensis) has two indistinct greyish saddles, and a smaller black band running through the fishes eye. The rear quarter of the fish is yellow, with a small black spot marking the base of the tail. It may also be referred to as the Pacific Double Saddle Butterflyfish
This fish is often confused with Chaetodon falcula from the Indian Ocean, usually known as the "true" Double Saddle Butterfly or Blackwedge Butterfly. The area between the black saddles is yellow on C. falcula and white on C. ulietensis. The saddles themselves are usually crisper on C. falcula and blurrier on C. ulietensis. This butterfly is known to eat anemones as well as corals and some other inverts.
Butterflyfish consist of a large number of fish found in the aquarium trade from the Chaetodon, Chelmon, Forcipiger, and Heniochus genuses, among others from the family Chaetodontidae. The family ranges in length from 3 inches up to close to 12 inches in length. Butterflies are usually roughly oval in body shape but longer fins make some appear elliptical or diamond-shaped. They resemble and are sometimes confused with angelfish (family Pomacentridae) but angelfish have a cheekspine that is not found in butterflies.
Butterflies are generally community fish in nature. Though some more pugnatious species may terrorize smaller or more docile fish, most can be kept with a wide range of community tankmates. Most butterfly species are not "reef safe" and will eat corals and polyps. In fact, some more delicate butterflies require corals as part of their natural diet. Butterflies may also harm smaller crustaceans (crabs and shrimp) and may pick at inverts like clams, feather dusters, anemones and similar tankmates. Use caution when introducing a butterfly into a tank with inverts; though some are considered "reef safe" by some aquarists, any butterfly may pose a risk to corals and inverts.
The diet of butterflies can vary, as mentioned, based on what they normally eat in the wild. Some very picky species only pick at coral flesh and can be difficult to wean onto an aquarium-based diet. A very varied diet of algae and meaty items like brine shrimp, mysis shrimp, scallops, clam, corals, sponges and other items is best. Vitamin supplements can also help get the butterflies all the nutrition they require. While some butterflies are very hardy and suitable for aquarists of all levels, more sensitive species should be attempted by experienced aquarists only.