While it looks like a butterflyfish, close inspection of the gill cover of the Singapore angelfish, or vermiculated angelfish (Chaetodontoplus mesoleucus) will confirm that it is indeed an angelfish. The Singapore angelfish is a very elegant-looking species that until recently was thought to exhibit two different tail fin colors — a yellow tail form and a gray tail form. Recent studies have demonstrated that these are two distinct species, the Singapore angelfish (Chaetodontoplus mesoleucus) and the graytail angelfish (Chaetodontoplus poliourus), both of which are available in the aquarium trade.
Difficulty: When it comes to its durability, the Singapore angelfish has a rather bad reputation. But this may be more a function of where and how the fish was collected and handled than an inherent hardiness issues with the species. If you can get a hold of a healthy Singapore angelfish specimen, Chaetodontoplus mesoleucus usually does very well in an established aquarium. Both the Singapore angelfish and graytail angelfish tend to acclimate more quickly and live longer in a reef aquarium, where they have plenty of algae and sessile invertebrates (encrusting sponges) to graze upon. If you have a fish-only aquarium, try cultivating a healthy crop of filamentous algae before adding a Singapore angelfish.
Physical description: The Singapore angelfish has a yellow head, white mid-body and a black rear half. The black area is also covered with white. As mentioned above, there are two species that can be distinguished by the tail color. The Singapore angelfish has a yellow tail and white pelvic fins. The graytail angelfish has a gray tail with yellow pelvic fins. Chaetodontoplus mesoleucus reaches a length of 6.5 inches.
Range: The Singapore angelfish is known from southern Japan south to Indonesia and Papua New Guinea. Interestingly enough, the Singapore angelfish is not known from Singapore! The Singapore angelfish is often found on coastal fringing reefs, as well as on reef faces and slopes on outer reefs. The reported depth range is less than 3 to at least 65 feet. Male Singapore angelfish occupy a territory that includes the home ranges of one or two females. As they roam about their “turf,” they nibble on algae, sponges, tunicates and may even nip at stony corals.
Compatibility: The Singapore angelfish is not considered to be an aggressive fish, but like many angelfish, it can become a bit cranky when “new” fish invade its aquarium territory. In most cases, the Singapore angelfish is likely to get most upset about fish similar in shape and color, such as other angelfish or butterflyfish. The Singapore angelfish is also more likely to pester newly added species that are non-related (e.g., gobies, firefish) if crowded. The best thing to do to avoid aggression is to have a larger aquarium. The Singapore angelfish can be kept in pairs in larger aquariums as well, but sexing can be tricky. Males will fight with one another, while females tend to other females. The Singapore angelfish is likely to be picked on by more aggressive angelfish in the genera Holacanthus and Pomacanthus. The Singapore angelfish is best added to the mixed-angelfish aquarium before more bellicose pomacanthids. While it can be housed in reef aquariums, an occasional individual may nip at coral polyps and clam mantles. The Singapore angelfish is less of a threat to treelike soft corals, such as Nephthea, Litophyton and Sinularia.
Aquarium conditions: Keep your Chaetodontoplus mesoleucus in a spacious aquarium (an aquarium of at least 100 gallons will suffice for a full-grown fish), with hiding places that they can dive into when frightened. Acceptable water parameters for the Singapore angelfish are: pH of 8.1 to 8.4, specific gravity of 1.019 to 1.025 and a water temperature of 76 to 82 degrees Fahrenheit.
Care considerations: The Singapore angelfish is always shy when initially added to the aquarium, thus, good refuges and non-combative neighbors will be essential to ensure acclimation. If picked on, the Singapore angelfish will not feed, and is likely to succumb to parasites or disease. The Singapore angelfish is occasionally afflicted with Cryptocaryon, Amyloodinium, Uronema and Lymphocystis.
Breeding: While not likely, it is possible that the Singapore angelfish will spawn in very large home aquariums.