Swallowtail Angelfish (Genicanthus melanospilus)

The Swallowtail Angelfish is the reef keeper's angelfish: genuinely, reliably reef safe, peaceful enough for community systems, and visually stunning in a way that rewards close attention. Genicanthus melanospilus, also known as the Spotbreast Angelfish or Blackspot Angelfish, belongs to a genus that stands apart from virtually every other angel in the hobby. Where most angelfish are benthic grazers that pose an ever-present risk to corals and invertebrates, Genicanthus are the only true zooplanktivores in the family, spending their days picking from the water column rather than picking at the rockwork. The female is a study in elegant contrast: a warm yellow dorsally, transitioning into a soft pale blue-white on the belly and flanks, finished with a deeply forked caudal fin edged in rich blue-black. That lyre-shaped tail and the fish's fluid, mid-water swimming style give it a grace that few other reef fish can match. This listing is for a female specimen, which makes an excellent standalone display fish and a natural starting point for anyone planning a mated pair or small harem down the line.

Why we love it

• One of the very few truly reef-safe angelfish available in the hobby; will not nip at stony or soft corals, sessile invertebrates, or clam mantles
• The only planktivorous angelfish genus, meaning its feeding behaviour in the aquarium is fundamentally different from and far more compatible with a reef than any other angel species
• Striking sexual dimorphism between male and female makes a pair or small group one of the most visually dynamic combinations in the reef fish hobby
• Peaceful, relatively tolerant social behaviour allows it to be kept singly, as a pair, or in a one-male harem if introduced correctly
• A protogynous hermaphrodite: if the male in a social group is lost, the dominant female will transition to take on the male role and colouration over time, adding biological interest to any long-term display
• Adapts well to aquarium life once settled, accepting a wide range of meaty and algae-based foods readily

Suggested parameters

• Temperature: 22–26°C (72–78°F)
• Salinity: 1.020–1.025 SG
• pH: 8.1–8.4
• Alkalinity: 8–12 dKH
• Ammonia/Nitrite: 0
• Nitrate: Under 10 ppm; as a deeper-water species from steep outer reef slopes and drop-offs, this fish appreciates the clean, stable water quality of a mature, well-maintained system

Care and temperament

• Difficulty: Intermediate
• Temperament: Peaceful with most reef fish; can show mild aggression toward small planktivores including fairy wrasses, flasher wrasses, firefish, and anthias, particularly if they are introduced into the tank after the Swallowtail is established
• Reef safe: Yes. One of the most consistently reef-safe angelfish available, with no documented tendency to nip at corals or sessile invertebrates
• Minimum tank size: 100 gallons minimum; 125 gallons or larger is strongly preferred given this species' active, open-water swimming nature and the importance of genuine swimming volume over raw footprint

Diet

Genicanthus angelfish are zooplanktivores, feeding in the wild from the open water column rather than grazing the substrate, and their aquarium diet should reflect that feeding strategy.

• Frozen mysis shrimp and vitamin-enriched brine shrimp as the dietary foundation
• High-quality angelfish preparations and marine-based frozen blends
• Spirulina-based pellets and flakes accepted readily by most settled individuals
• Marine algae and seaweed sheets as a supplement; this species benefits from a varied diet that includes both meaty and algae-based components
• Feed small portions 2 to 3 times daily; multiple small offerings suit its natural planktivorous feeding style far better than a single large daily feeding

Compatibility and tankmates

• An excellent community reef fish, compatible with tangs, larger wrasses, clownfish, gobies, basslets, cardinalfish, and most other peaceful to semi-aggressive species
• Can be kept singly, as a bonded male-female pair, or as one male with multiple females introduced simultaneously; the one-male-per-system rule is firm, as males are aggressive toward other males and toward other Genicanthus species
• Use caution when pairing with small planktivores including anthias, firefish, dartfish, and fairy wrasses, as these may be harassed; in a sufficiently large system with ample territory, coexistence is often possible but should be monitored
• Not suitable with aggressive species that will bully or outcompete it at feeding time
• Pairs and harems must be introduced simultaneously; adding a female to an established male, or a second female to an established group, carries significant aggression risk and should be approached with care

Health and acclimation notes

The Swallowtail Angelfish is considered one of the more adaptable and durable reef angelfish once settled, but it does come from deeper reef zones, typically 20 to 45 metres, and appreciates a system with shaded areas, overhangs, and dimly lit refugia in the rockwork, particularly during the first weeks of introduction. Good water movement throughout the tank is important for this active, column-swimming species. Like all angelfish, it carries a cheek spine that can catch in netting and cause injury; always use a container rather than a net when transferring or handling. Quarantine before introduction to an established display is always recommended. As a protogynous hermaphrodite, all individuals begin as females and the dominant fish transitions to male when a male is absent; females purchased now can be paired with a male at any point, or a dominant female may naturally transition if kept as a group without a male over time.

What you are buying

• You will receive: 1 Swallowtail Angelfish, female (Genicanthus melanospilus)
• Females display a warm yellow dorsal colouration transitioning to pale blue-white on the belly and flanks, with a deeply forked caudal fin edged in blue-black
• Colouring intensity and the prominence of the tail edging can vary between individuals and by region of origin
• Size may vary; please see size options at checkout