Swallowtail Angelfish (Spotbreast Angelfish)

Characteristics, Origin, and Helpful Information for Hobbyists

Swallowtail angelfish (Genicanthus sp.), front view

Dorling Kindersley / Getty Images

Something that is unique about this type of angelfish is that it will usually leave coral alone, making them suitable for reef tanks. This species can get up to 7 inches long and prefers a lot of swimming space, so you will need to get a larger tank, at least 125 gallons, to house this fish.

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


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

Colors and Markings

This fish 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. 

Beyond its crescent-shaped caudal fin, a few other notable characteristics are found throughout this species. They 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 the encrusting rubble.


Matching swallowtails with potential tank mates is an area requiring more concern and effort than does their diet. Swallowtails will not overtly attack the vast majority of fish, as they are rather peaceful themselves, but it may chase after small peaceful planktivores or get harassed by other planktivores.

Be careful not to mix swallowtail angels with fish that are outwardly more aggressive. They can, and most certainly will be dominated by larger aggressors. Such aggressive fish would include triggerfish, large angelfish, and most surgeonfish. Likewise, thought should be given prior to introducing any additional planktivores, like Anthias species, with the swallowtails.

Males will fight with males from its species, other Genicanthus genus males, and those fish that have similar coloration. It might be best to keep this fish alone, as a mated pair, or you can keep a small group of females with one male in a larger aquarium. Typically, it ignores other fish species including non-related angelfish. Possible tankmates include clownfish, blennies, gobies, chromis, butterflyfish, small lionfish, and eels.

Habitat and Care

In the aquarium trade, the swallowtail angelfish is considered a difficult shipper. But if you can find a healthy specimen, it settles 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 this fish lots of hiding places and live rock for grazing. 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 tank 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.


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 and marine algae-based foods, such as finely chopped fresh shrimp and frozen silversides, frozen brine and mysis shrimp, angelfish preparations, dried seaweed (nori), enriched flakes, or pellets containing spirulina.

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

Sexual Differences

This is one of a few angelfishes that can easily be identified by sex as male or female, because of their differences in appearance. Males have a considerably different coloration or pattern than females. The male is marked with thin, dark vertical bands that cover the body from the head to where the dorsal and anal fins end, followed by a yellow-banded area at the base of the tail, and thus named a zebra angelfish.

This species of fish is known as a protogynous hermaphrodite, which means this fish will adopt the male coloration and become a male-only after first living as a functional female for a period of time. When the opportunity arises, most often from the lack of a dominant male's presence, the dominant female of the local group will become male. Swallowtails reportedly take up to 30 days to complete this sex change.


Males entice females to mate with a number of different movements or fin gestures. Swallowtail 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, 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 separated by only a few inches, roll onto their sides and release their eggs and sperm. 

More Pet Fish Breeds 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.