Astyanax bimaculatus Care Guide
Astyanax bimaculatus is a hardy, widespread South American tetra named for the dark spots on its shoulder and caudal base.
Compiled by Aquairi from published sources · Published · Updated
Overview
Astyanax bimaculatus is a freshwater characin first described by Linnaeus in 1758. It is recognised by two strong dark markings: a humeral spot on the shoulder and a second blotch of pigment at the base of the caudal fin. FishBase reports a maximum length of about 17.5 cm and a maximum recorded weight near 92 g, with females growing larger than males.
Taxonomy
- Family: Characidae
- Genus: Astyanax
- Scientific name: Astyanax bimaculatus
- Originally described as Salmo bimaculatus (Linnaeus, 1758)
Habitat
The species has an extensive distribution across South America, from Panama through the Amazon basin and into the Orinoco and numerous other river systems. According to FishBase it inhabits large free-flowing clear rivers, small streams, drainage ditches, and artificial ponds and impoundments, showing a marked tolerance for variable conditions.
Tank requirements
- Minimum tank volume: 200 L
- Temperature: 18-28 °C (64-82 °F)
- pH: 6.0-7.8
- GH: 4-18 °dGH
- School size: 6 or more individuals
- Lifespan: 5-8 years
Diet
Astyanax bimaculatus is an omnivore. FishBase records that it feeds on zooplankton, detritus, higher plants and at times the scales of other fish, with a trophic level near 2.4. Dietary studies cited on Wikipedia describe a mixed diet of roughly 60% plant matter and 40% animal matter, with insects the most common animal prey.
Compatibility
This is an active, mid-water schooling tetra that is best kept in a group in a larger tank. It can be semi-aggressive and may consume scales or fins of much smaller tankmates, so it is better matched with robust companions of similar or larger size rather than small, delicate fish.
Breeding
The species is an egg-scatterer capable of year-round reproduction, with spawning reported to peak around January and February. FishBase notes that gametogenesis takes place during the dry season so that reproduction begins with the rains, and spawning has been achieved in captivity.
Conservation status
IUCN Red List: Least Concern (assessed 4 March 2021).
Two-spot Astyanax (Astyanax bimaculatus) Breeding Guide
Overview
Astyanax bimaculatus is a large, hardy and widely distributed characin found from Panama to the Amazon basin, reaching up to about 17.5 cm. It is named for its two dark marks: a strong humeral (shoulder) spot and a blotch at the base of the caudal fin. It is an egg-scattering species; gametogenesis takes place in the dry season so reproduction can begin with the rains, and spawning has been achieved in captivity.
Sexing
Sexes are best told apart by body condition in mature fish, with egg-laden females appearing rounder. Detailed external dimorphism is not described in the consulted sources.
Conditioning
Given the adult size, use a large, well-filtered tank and condition the fish on a varied diet. Because the species is capable of year-round reproduction with a peak in January and February, and is least active in May to July, conditioning is most effective approaching the natural spawning peak.
Breeding Setup
- A large spawning tank suited to a tetra of up to about 17.5 cm.
- Soft to moderately hard water within the species range (pH 5.5-7.5, up to about 25 dH, roughly 20-28 C).
- Areas of low water current, since the eggs are laid in calm water.
- Fine-leaved plants or a protective base to receive the scattered eggs.
Spawning Behavior & Trigger
The eggs of A. bimaculatus are weakly adhesive and are laid in environments of low current. The species can reproduce year-round, with the spawning peak in January and February, and it is less likely to be in active reproductive condition during May, June and July. Mimicking the onset of the rainy season helps trigger spawning.
Common Challenges
As an egg-scatterer the adults may consume the eggs, so a protective spawning medium or removal of the adults is advisable. The large adult size demands ample tank space, and detailed fecundity figures are not given in the consulted sources.