Swallowtail Angelfish: Fish Species Profile

Characteristics, Origin, and Helpful Information for Hobbyists

Swallowtail angelfish (Genicanthus sp.), front view

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The swallowtail angelfish is a member of the lyretail angelfish genus (Genicanthus spp.), named for the shape of their tails, which resembles a U-shaped harp instrument called a lyre. The swallowtail species is specifically named for its tails' butterfly-like appearance.

Tails aside, the swallowtail is unique among angelfish species in that it does not pick food out of coral crevices, making it suitable for reef tanks because it will not destroy the coral. This angelfish can get up to seven inches long and prefers a lot of swimming space, so you will need a large tank—at least 125 gallons—to house a swallowtail.

Breed Overview

Common Names: Black-spot angelfish, spotbreast angelfish, Japanese swallowtail angelfish, blackspot lyretail, and zebra angelfish

Scientific Name: Genicanthus melanospilos

Adult Size: 7 inches

Life Expectancy: 10 to 15 years

Characteristics

Family Pomacanthidae
Origin Western Indo-Pacific, Australia
Social Peaceful
Tank Level All areas
Minimum Tank Size 125 gallon
Diet Omnivore
Breeding Egg scatterer
Care Moderate
pH 8.1 to 8.4
Hardness 8 to 12 dGH
Temperature 72 to 78 F

Origin and Distribution

This angelfish species is found around Fiji, Indonesia, and Vanuatu islands in the Pacific Ocean. This species inhabits moderate to deep waters on steep slopes. A single male is usually seen with several females. 

Colors and Markings

The swallowtail angelfish is also called a blackspot angelfish because of the black spot located on the male's breast. The female is yellow dorsally and light blue ventrally. The caudal fin is marine-blue highlighted by a dark, blue-black edging on the top and bottom. The male is marked with a series of vertical red stripes covering the entire pale-colored body. The tail of the male is forked and is yellow with blue edges. 

Swallowtails have small mouths lined with three or four rows of small bristle-like teeth, often with tips that have three points. Their teeth are shorter than the rest of the members of the Pomacanthidae family, obviously a reflection of their feeding tactics of picking prey out of the water column versus removing algae from coral's encrusting rubble.

Tankmates

Swallowtails will not attack the vast majority of fish, as they are rather peaceful themselves, but may chase after small peaceful planktivores like Anthias fish.

Be careful not to mix swallowtail angelfish with fish that are outwardly aggressive. They may be dominated by larger aggressors. Such aggressive fish include triggerfish, large angelfish, and most surgeonfish.

Males will fight with males from their species, other Genicanthus genus males, and those fish that have similar coloration. To avoid problems, keep this fish alone, as a mated pair, or as a small group of females with one male in a larger aquarium.

Ideal tankmates include clownfish, blennies, gobies, chromis, butterflyfish, small lionfish, and eels.

Swallowtail Angelfish Habitat and Care

In the aquarium trade, the swallowtail angelfish is considered fragile and therefore difficult to ship. But, if you can find a healthy specimen, it will settle into aquarium life rather quickly. 

Because of its size and constant roaming nature, the minimum aquarium size suggested for this fish is at least 125 gallons. You should offer lots of hiding places. This type of angelfish makes a good reef dweller that will not nip at stony and soft corals (sessile invertebrates). 

Provide areas of strong water movement in the aquarium during the day. Use pumps on timers that can be turned off after 8 to 10 hours. Well-oxygenated water is optimal. Lids are necessary as this fish may attempt to jump out of open aquariums.

Swallowtail Angelfish Diet and Feeding

Naturally a planktivore, this is an angelfish that often dines on diatom and filamentous algae in aquariums. It should be fed a varied diet of meaty fares, such as finely chopped fresh shrimp and frozen silversides, frozen brine and mysis shrimp, and marine algae-based foods such as dried seaweed (nori), enriched flake food, or pellets containing spirulina that are suitably sized for angelfish.

This fish will gulp food from the water's surface and may swallow air at the same time. It is not unusual for the fish to become bloated, resulting in it appearing to be struggling while swimming head down. But don't worry, it gets rid of this trapped air by expelling bubbles from its mouth and anus. In other words, it burps and farts. Feeding sinking food will help prevent it from ingesting air at the surface.

Gender Differences

This is one of a few angelfishes that can easily be identified as male or female, because of their distinct differences in appearance (called sexual dimorphism).

The male is marked with thin, dark vertical bands that cover the body from the head to where the dorsal and anal fins end. It has a yellow band at the base of the tail.

The female is blue, fading from darker at the head to lighter near the tail. The dorsal fin is mostly yellow, fading into the midsection of the body. The white tail is outlined in black. 

This species of fish is known as a protogynous hermaphrodite, which means it is a female when it hatches. Then, if there is no dominant male presence in the immediate environment, the dominant female of the local group will spontaneously become a male. Swallowtail angelfish reportedly take up to 30 days to complete this sex change.

Breeding the Swallowtail Angelfish

Males entice females to mate with several different movements or fin gestures. Swallowtail angelfish males roll onto their sides or backs in front of females, or position themselves directly in front of the female and tremble or quiver their caudal fin. If the male is successful in his initial attempts to lure a female, he continues the mating ritual.

While positioned alongside the female, the male's entire body will vibrate or quiver excitedly. The female will then extend all of her fins as a sign of encouragement. After a few seconds of the male nuzzling his head near the rear of the female, the pair will roll onto their sides and release their eggs and sperm. 

More Pet Fish Species and Further Research

If swallowtail angelfish appeal to you, and you are interested in some compatible fish for your aquarium, read up on:

Check out additional fish breed profiles for more information on other saltwater fish.