The Declivis Butterflyfish (Chaetodon declivis) is a compact, strikingly marked species from the Central Pacific, where it is known from the Marquesas and Line Islands, including Kiritimati. The silvery-white body carries rows of black spotting, a yellow band crossing the eye, and yellow tail, with yellow-to-orange color washing the upper rear body and dorsal region. The species name refers to the abrupt, sloping diagonal where that upper coloration meets the pale flanks, a feature that makes identification straightforward. Adults reach roughly 5 inches, small for a Chaetodon, and in the wild they range across reefs as well as adjacent rocky and sandy bottoms.

Adult housing should begin at 120 gallons. Published guidance for this fish ranges from 70 gallons upward, but the larger footprint better suits its need for both uninterrupted swimming lanes and a complex reef structure to work over. Build substantial rockwork that offers grazing surfaces, shaded overhangs, and several separate retreats, then leave generous open water in front of it. A well-established, mature system is important, since newly acquired specimens can be reserved and benefit from stable conditions and plenty of visual cover. Care level is moderate, largely because feeding response and long-term nutrition demand attention rather than because the fish is delicate in a settled tank.