Black Oscar (Astronotus crassipinnis) Breeding Guide

Breeding Astronotus crassipinnis: a monomorphic biparental substrate spawner from the southern Amazon and Paraná-Paraguay basins.

Overview

Astronotus crassipinnis is an oscar relative reaching up to about 25 cm, found in the southern Amazon basin and the Paraná-Paraguay basins. It is very rare in the aquarium hobby, where it is sometimes called the "fat oscar". Detailed breeding accounts are scarce, so the reproductive behaviour described here follows the genus Astronotus (the oscar), of which it is a member.

Sexing

Oscars are widely regarded as sexually monomorphic, so external sexing is unreliable; males may grow faster and some strains show dark blotches at the dorsal-fin base. Pairs typically reach sexual maturity around one year of age.

Conditioning

Keep a group of young fish and allow a pair to form, then condition the pair well. In the genus, frequency and timing of spawning may be related to the occurrence of rain, so cooler, softer water changes can help bring fish into condition.

Spawning Behavior & Trigger

Oscars are biparental substrate spawners. A pair selects and cleans a generally flattened horizontal or vertical surface before spawning. Fecundity scales with female size: smaller females lay around 300-500 eggs, while larger females may lay roughly 2,500-3,000.

Egg & Fry Care

Both parents guard the eggs and resulting fry, as is typical of cichlid brood care. As the fry grow they can be moved to and herded around the substrate by the parents until they are free-swimming and feeding.

Common Challenges

Because the species is monomorphic, obtaining a true pair without venting or letting a group pair off is difficult. Its large adult size demands a very large tank, and the rarity of A. crassipinnis means breeding stock is hard to source.