All fish / Pomacanthidae

Japanese Swallowtail Angelfish

Genicanthus semifasciatus

Also known as japanese swallow angelfish, japanese swallowtail, halfbanded angelfish, masked swallowtail angelfish, yes, トサヤッコ, 半带燕尾神仙, 日本燕尾神仙

Females are pale grey with a black edge running along the dorsal fin and tail. Males turn yellow on the face and belly and grow dark half bars along the flanks, so the two sexes look very different. People keep it because it is one of the more colourful swallowtail angels, and it feeds in open water instead of grazing coral.

Care at a glance

Care level

Moderate

Temperament

Semi

Adult size

20 cm

Temperature

22 to 26 °C

pH

8.1 to 8.4

Smallest tank

500 litres

Keep as

Singly, or one male with one or more females in a large tank

Diet

Omnivore: mysis, krill, chopped seafood, plankton substitutes, spirulina and quality marine flakes or pellets

Swims

Middle of the tank

Lifespan

5 to 10 years

Water

Marine (saltwater)

Wild range

Western Pacific: southern Japan, Taiwan and the Philippines

Breeding

Like other swallowtail angels it is a protogynous hermaphrodite, which means a dominant female can change into a male. Pairs spawn in open water at dusk and the eggs drift. Captive breeding is very rare and the young are hard to rear.

Good to know

It needs a large tank with plenty of swimming room, and two males in one system will fight. Wild fish caught deep sometimes ship badly, so look for one that is already feeding well before you buy.