For dedicated marine aquarists seeking a challenge, five rare fish species stand out for their unique adaptations and demanding care requirements. These fish, sourced from the Western and South Pacific and other regions, are not for beginners. They require specific water conditions, diets, and tank setups to thrive.
Among these is the Colin's Angelfish (Paracentropyge colini), a vibrant species with a yellow body and blue-to-black markings on its head and anterior dorsal fin. Native to deep waters, it is rarely captured due to its ability to hide. In an aquarium, this angelfish prefers dimmer environments and will graze on macro-algae, though it may nip at corals. Its shy nature means it should be introduced before more aggressive tank mates.
Another extraordinary species is the Flashlight Fish (Anomalops katoptron), also known as the Two-fin Flashlight Fish or Lantern Fish. This nocturnal dweller has a unique light-producing patch under each eye, filled with bioluminescent bacteria. This symbiotic relationship allows the fish to emit a glow, which it can blink on and off for communication, predator distraction, and attracting zooplankton. Flashlight fish are peaceful and do well in groups, making them suitable for a low-light aquarium with plenty of hiding spots. They are not bred in captivity and are rare due to their ability to hide in dark waters.
For those interested in syngnathids, the Yellow Multibanded Pipefish (Doryhamphus pessuliferus) offers a colorful addition. With bright yellow and deep red rings, this pipefish is a visual standout. However, like many seahorses and pipefish, it is sensitive to water quality and can be a picky eater, often succumbing to Mycobacterium infections if weakened during transport. It thrives in peaceful communities, preferably in pairs or groups, and cannot be kept with aggressive fish, stinging anemones, or soft corals.
Bottom-Dwelling Rarities
The Fingered Dragonet (Dactylopus dactylopus) is a rare bottom-dweller that resembles a scooter blenny, with a dramatic dorsal fin and bright blue spots on its head and anal fin. It burrows in sandy substrate and feeds on tiny live foods like mysis, which can be cultivated in a refugium. Multiple dragonets can be kept together if introduced simultaneously to avoid competition for burrows and feeding spots. This species is rare due to its ability to hide among the reef and its picky eating habits in captivity.
Perhaps the most elusive is the Peppermint Angelfish (Paracentropyge boylei), a white and red banded species that is exceptionally rare. As of March 2019, only one was on public display at the Waikiki Aquarium. Reaching a maximum length of 2.5 inches, it is considered the most expensive reef fish per inch. For those fortunate enough to acquire one, a large aquarium of at least 125 gallons is required, and it should be fed like other marine angelfish.
These five species represent the pinnacle of marine aquarium keeping, offering both beauty and challenge. They require a commitment to maintaining pristine water conditions and providing appropriate diets, but for expert aquarists, the rewards are unmatched.