Taxonomy & naming
Ctenopoma ocellatum was described by the French ichthyologist Jacques Pellegrin in 1899. The type locality is Makaka in the Democratic Republic of Congo, and the holotype is held at the Muséum national d'Histoire naturelle in Paris (MNHN 1886-0472). Eschmeyer's Catalog of Fishes confirms the valid name as Ctenopoma ocellatum Pellegrin, 1899.
A name that appeared in the same publication, Ctenopoma denticulatum Pellegrin, 1899 (type locality Congo, holotype MNHN 1890-36), is now treated as a junior synonym of C. ocellatum, a synonymy documented in the Africa Museum (Faunafri) taxonomy records. The species is placed in the family Anabantidae (the climbing gouramies sensu lato) within the order Anabantiformes.
The genus Ctenopoma, established by Peters in 1844, is a grouping of medium-sized African climbing perches. The specific epithet ocellatum is Latin for 'adorned with a little eye', referring directly to the prominent ocellus — an eye-shaped spot — that decorates the caudal peduncle of this species.
Morphology
Ctenopoma ocellatum is a moderately elongate, laterally compressed labyrinth fish. FishBase records maximum sizes of 5.5 in standard length in males and 5.5 in SL in females, making it one of the larger members of its genus. The body is deepest through the midriff and tapers toward the caudal peduncle. The head is relatively large with a slightly upturned, oblique mouth suited to seizing prey from above or below.
The body is covered in ctenoid scales, and the opercle bears small spines — a feature shared across the genus. Coloration is typically muted: a brown to olive-grey base with faint dark blotching or banding that blends well into leaf litter and vegetation. The diagnostic feature is the ocellus at the upper base of the caudal fin — a sharply defined black spot enclosed in a pale or silvery ring — which gives the species its common name and scientific epithet.
Sexual differences are subtle; females may be slightly deeper-bodied when gravid, but the species lacks the strongly contrasting coloration seen in some other anabantids. Both sexes share the suprabranchial labyrinth organ, the accessory air-breathing apparatus that allows the fish to survive in poorly oxygenated water.
Habitat
Ctenopoma ocellatum occurs in two geographically separated regions: the middle Congo River basin (Democratic Republic of Congo and Republic of Congo) and the Niger Delta of Nigeria. It is a freshwater benthopelagic species, described by FishBase as an obligate air-breather, a trait typical of the family Anabantidae.
In the Congo system the species inhabits slow-moving or still waters associated with the extensive forest drainage — backwaters, flooded marginal zones, and streams with dense submergent and emergent vegetation. The leaf-strewn substrate and dense plant cover match the fish's ambush hunting mode and cryptic coloration. FishBase records water conditions of 75–82 °F and pH 6.0–7.5, with hardness in the range of 5–12 dH, reflecting the soft, mildly acidic character of much Congo Basin water.
As an obligate air-breather, C. ocellatum must have unimpeded access to the water surface to breathe atmospheric air through its labyrinth organ, and it tolerates the naturally low dissolved-oxygen conditions of warm, still, vegetated tropical waters better than purely gill-breathing fish can.
Feeding
Ctenopoma ocellatum is a carnivore. FishBase records the diet as insects and small crustaceans, consistent with the hunting behaviour typical of larger Ctenopoma species: a patient, ambush-oriented predator that waits motionless among cover and lunges at prey that ventures within range.
In common with other ctenopomas, it likely feeds opportunistically on whatever animal prey is available at an appropriate size — aquatic insect larvae, small crustaceans, worms, and possibly small fish. The oblique, upward-angled mouth is well suited to intercepting prey near the surface or from below.
In the aquarium, C. ocellatum should be offered meaty foods: live or frozen bloodworm, brine shrimp, small earthworms, river shrimp, and similar items. Many specimens from the wild are reluctant to take prepared dry foods, though some individuals can be weaned onto larger pellets over time. Feeding at dusk or in low light can encourage shyer fish to come forward.
Mating
Detailed courtship and spawning observations for Ctenopoma ocellatum in the wild are sparse in the published literature. Within the genus Ctenopoma, reproductive strategies vary by species, and some members are known to scatter buoyant eggs into open water with no parental care. Based on available data and analogy with related species, C. ocellatum is considered an open-water egg-scatterer.
In species of this type, males may display to females using fin-spreading and body posturing, but there is no nest construction and no territorial guarding of eggs. Where observations exist for the genus, spawning tends to occur near the surface, with eggs released in small numbers and left to drift freely. The ocellus on the tail may play a role in intraspecific signalling, though its primary function is generally interpreted as a deflection marking against predators.
Breeding
Ctenopoma ocellatum is not commonly bred in captivity, and detailed accounts in the hobbyist literature are limited. In genera where open-water egg-scattering is the reproductive mode, the eggs are typically buoyant or semi-buoyant and receive no parental investment after release; adults may consume eggs given the opportunity.
For aquarists attempting to breed it, the approach used for other open-water-spawning anabantids is a reasonable starting point: a well-conditioned pair or trio, a spacious tank with subdued lighting and dense planting or spawning mops near the surface, and a temperature in the upper part of the preferred range (79–82 °F). Water that is soft and slightly acidic matches the Congo Basin conditions. Any eggs or fry should be removed promptly to a separate rearing vessel. Fry of similar species are initially tiny and require infusoria or rotifers before graduating to nauplii.
The limited breeding data available for this species means aquarists should treat any captive spawning as a novel contribution to knowledge of the species.
In the aquarium
Ctenopoma ocellatum is an infrequent but genuinely interesting aquarium fish, more suited to the specialist than the community aquarist. Its size — up to 5–5.5 in — means it will consume smaller tankmates, and its ambush predator temperament means it spends much of the day motionless among cover rather than swimming actively in the open. A biotope-style setup with West African river character — brown, tannin-stained water, a soft substrate, driftwood, leaf litter, and live or artificial plants — suits it well and shows off its camouflage coloration.
Water parameters should follow the Congo Basin baseline: 75–82 °F, pH 6.0–7.5, moderate softness. As a labyrinth fish it must be able to reach the surface; keep the aquarium covered and ensure there is a warm air gap between the water surface and the hood to avoid chilling the labyrinth organ when the fish surfaces to breathe. Filtration should provide clean water without strong current — this is a still-water species.
Compatible tankmates are robust fish of similar or larger size that cannot be swallowed and that tolerate the same water conditions. Other similarly sized West African species — larger characins, other Ctenopoma, or peaceful cichlids of compatible size — are candidates, though tankmate compatibility should be assessed individually. Multiple Ctenopoma ocellatum can sometimes be housed together in large, well-decorated tanks with ample line-of-sight breaks.
Conservation
Ctenopoma ocellatum is assessed as Least Concern (LC) on the IUCN Red List, evaluated by Lalèyè and Moelants in 2009. The assessment reflects a species with a moderately wide distribution across two major river systems — the middle Congo basin and the Niger Delta — without evidence of rapid population decline or severe habitat restriction at the time of assessment.
The middle Congo River basin is one of the world's great freshwater ecosystems, and much of it remains relatively intact compared with other tropical river systems, though deforestation, artisanal fishing, and extraction pressure are ongoing concerns across the basin. The disjunct Niger Delta population faces a more immediately modified habitat, as the delta has been subject to significant anthropogenic pressure from oil extraction and associated pollution, agriculture, and urban development.
The species is collected for the ornamental trade in small numbers. Its relatively low profile in the hobby means it is not subject to the same collection pressure as more popular species, but aquarists sourcing it should verify that specimens are responsibly collected or, where possible, captive-bred.