Japanese swallow angelfish (Genicanthus semifasciatus) care guide

Group
Marine fish
Other names
Japanese swallow
Family
Pomacanthidae (marine angelfishes)
Origin
Western Pacific, southern Japan (including Izu, Ogasawara and Ryukyu Islands) to the northern Philippines; seaward reefs, 15–200 m
Water
saltwater
Maximum size
21 cm
Temperature
24–27°C
pH
8.1–8.4
Hardness
Salinity SG 1.023–1.026
Minimum tank
500 litres
Care level
intermediate
Temperament
peaceful
Reef safe
yes

Care

Needs open swimming room above the rockwork and good water flow. The minimum tank size of about 500 litres is our own estimate from the adult size and habits, not a figure from the sources. No species-specific water figures are given in the sources, so the values here are general marine aquarium guidance rather than figures for this fish: 24–27 °C, pH 8.1–8.4 and a specific gravity of 1.023–1.026. Keep conditions stable, with low nitrate and good oxygenation. Lives in harems of one male and several females. A midwater swimmer that is gentler than most angelfish. Females are greyish with a yellow face and a swallow-like tail; males have black and tan bars on the back, a yellow blaze from the mouth and a bluish-grey underside. Uncommon in the trade; most fish come from the Philippines. IUCN: Least Concern. Sources: Wikipedia, List of marine aquarium fish species (en.wikipedia.org/wiki/Listofmarineaquariumfishspecies); Wikipedia (en.wikipedia.org/wiki/Genicanthussemifasciatus). Checked October 2026.

Diet

Picks plankton from open water. Offer several small feeds a day of frozen mysis, enriched brine shrimp, finely chopped seafood and quality marine flakes and pellets.

Breeding

Marine angelfish are pelagic broadcast spawners: a pair rises into the water column, usually around dusk, and releases eggs and sperm together. Protogynous hermaphrodite that lives in harems. Rarely spawned in aquaria.

Compatibility and tank mates

Listed as reef safe: it feeds in the water column and does not normally nip corals. Keep one male with one or more females alongside other peaceful planktivores.

Last updated 8 October 2026. Community-edited care guide on Aquatic-Auctions.

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