Taxonomy & naming
The species was described by George Albert Boulenger in 1905 in the Annals and Magazine of Natural History (series 7, volume 16, pages 640–642), in a short paper titled 'On a small Collection of Fishes from the Kasai River (Congo).' Boulenger placed it in Paratilapia, then a sprawling catch-all genus into which a great many African cichlids with a particular tooth and lateral-line arrangement were provisionally dumped — a usage entirely separate from the Malagasy Paratilapia that the name properly denotes today. The description rests on a single fish, the holotype (register MRAC 1346, in the Royal Museum for Central Africa at Tervuren), collected at Lusambo on the Sankuru–Kasai system. No additional specimens or populations have been reliably reported since, so the species is effectively known from that one individual and that one locality. Its generic placement has never been resolved: Eschmeyer's Catalog of Fishes lists it as valid but tentatively transfers it to Haplochromis (Boulenger 1905), following a 2011 note by R. Morgenstern, while flagging that this assignment is provisional. FishBase echoes the uncertainty, keeping the name under Paratilapia but cautioning that the genus is endemic to Madagascar and that toddi's true affinities are unknown — it sits, for now, in the African haplochromine tribe by default rather than by demonstrated relationship. In practice the fish floats between two names, Haplochromis toddi and Haplochromis toddi, neither of which is thought to capture where it actually belongs. A proper revision would require fresh material the species has never yielded.
Morphology
Haplochromis toddi is a small cichlid: FishBase gives a maximum length of about 6 in total length, based on the original material, and there is no evidence it grows appreciably larger. Beyond that figure, the published morphology is limited to Boulenger's terse 1905 diagnosis, which characterised the fish by standard cichlid counts and proportions rather than by any striking external feature — there is no preserved colour photograph, and the single museum specimen is long since faded. The fish presents as a generalised, moderately elongate haplochromine-type cichlid with the usual single continuous dorsal fin, a slightly oblique mouth, and a body form consistent with a small, generalist riverine predator rather than a specialised rock-grazer or sand-sifter. Coloration in life is undocumented; any description of pattern would be guesswork, and the species is not represented in the aquarium trade in a way that would have generated reliable live images. Sexual dimorphism has likewise never been described, because the type series does not include a confirmed, contrasting pair and no field study has examined breeding adults. In short, almost everything beyond the basic size and the family-level body plan is genuinely unknown, a reflection of how thin the original collection was and how little the fish has been encountered since.
Habitat
The species is known from a single point: Lusambo, on the Sankuru River where it joins the wider Kasai drainage of the central Congo River basin, in the Democratic Republic of the Congo. The Kasai is one of the Congo's great southern tributaries, and the surrounding region — the FEOW Kasai freshwater ecoregion, an area of roughly 900,000 square kilometres — is a mosaic of tropical floodplain rivers, swamp forests, savanna threaded with gallery forest, and peat-rich wetlands, all eventually draining north into the Congo mainstem. FishBase classifies toddi as a freshwater, benthopelagic species of tropical lowland rivers, and the IUCN assessment files it under inland wetlands. No in-situ water chemistry, depth, or biotope data exist for the species specifically; the Kasai system as a whole carries warm, soft, often tannin-stained blackwater to clearwater, with the chemistry varying by tributary and season. Because the fish has not been recollected, its real distribution is unknown — it may be a narrow endemic of the Sankuru–Kasai confluence, or it may simply be an under-sampled species of a vast and poorly surveyed basin whose ichthyofauna, despite holding well over a thousand fish species, remains incompletely catalogued. The honest position is that we know one river, one town, and very little else.
Feeding
There are no published gut-content data, field-feeding observations, or captive-diet records for Haplochromis toddi. What can be said is inferential. FishBase estimates a trophic level of about 3.3, the value expected for a small carnivorous-to-omnivorous cichlid, and the fish's general body form — a moderately elongate, normally-mouthed haplochromine-type — is that of a versatile riverine predator rather than a dietary specialist. By analogy with the many small generalist cichlids of the Congo's floodplain rivers and tributaries, toddi most plausibly takes aquatic insect larvae, small crustaceans, worms, and other benthic invertebrates, supplemented opportunistically by small prey and organic matter worked from the substrate and leaf litter. None of this is documented for the species itself; it is the reasonable expectation for a fish of this size, shape, and habitat, and it should be read as inference, not record.
Mating
Nothing has been recorded about how Haplochromis toddi pairs, courts, or holds territory. The species has not been observed alive in the wild in any documented study, and there is no established aquarium strain whose behaviour might fill the gap. The wider haplochromine assemblage of Africa contains both biparental substrate spawners and maternal mouthbrooders, and without specimens of known sex, gonad data, or behavioural observation it is not possible to say which strategy toddi follows, let alone describe its courtship or social structure. Any statement about its mating behaviour would be invention. The accurate summary is that the reproductive biology of this fish, from pair formation through to spawning behaviour, is entirely undescribed.
Breeding
The breeding biology of Haplochromis toddi is undocumented. No clutch size, spawning mode, egg description, parental-care pattern, or larval account has been published for the species, and it is not bred in captivity. FishBase's reproduction summary carries no substantive data beyond a generic family reference. Because the fish's very genus is unsettled — it is neither a confirmed Malagasy Paratilapia (which are biparental substrate spawners that guard their fry intensively) nor a verified member of any particular African lineage — even an analogy-based statement risks asserting the wrong reproductive guild. The small African haplochromines with which toddi is provisionally grouped are predominantly maternal mouthbrooders, but applying that to toddi specifically would be an unsupported guess. The truthful position is that this species has never been observed reproducing, in the wild or in aquaria, and its breeding mode remains unknown.
In the aquarium
Haplochromis toddi is not an aquarium fish. It has no presence in the ornamental trade, no documented captive-husbandry history, and no breeding records, and it is known to science from essentially a single old museum specimen. Hobbyists searching for 'Paratilapia' in the trade will instead encounter the Malagasy species — the 'starry night' or 'black diamond' Madagascar cichlids, Paratilapia polleni and the form sold as Paratilapia 'bleekeri' — which are real, keepable, and entirely different fish from this obscure Congo-basin namesake. Those Malagasy fish are large, predatory, intelligent biparental spawners that need spacious tanks, robust filtration, and careful tankmate selection, and most of the husbandry advice circulating under the genus name applies to them, not to toddi. For toddi itself there is simply nothing to keep and nothing reliable to recommend; any care sheet purporting to cover this species would be extrapolating from unrelated fish. If material ever did reach an aquarist, it would have to be treated as an experimental, undescribed Congo riverine cichlid — warm, soft, well-oxygenated water in the mid-20s Celsius, a generalist invertebrate diet, and close observation — but that is a hypothetical, not established practice. The honest entry here is that this fish has never been kept, and presenting otherwise would mislead.
Conservation
The IUCN Red List assesses Haplochromis toddi as Data Deficient (assessed 16 February 2009 by T. Moelants, published 2009). The category reflects exactly the situation described above: the species is known only from its type locality at Lusambo on the Kasai River, no population information exists, and its true range and ecology are unknown, so there is no basis for assigning a threat category. The assessment does, however, flag the pressures bearing on the small rivers of this part of the Congo basin. Artisanal but very intensive diamond mining is identified as an important threat: the sand excavated from riverbeds drives heavy sedimentation that degrades the in-stream habitat, and in the southern Kasai region industrial copper mining adds further pollution and disturbance. No conservation actions are in place, and the species occurs in no documented protected area. Against this backdrop, a fish known from one specimen at one mining-affected locality is impossible to assess properly and could in principle be at real risk without anyone being in a position to detect a decline — which is precisely why 'Data Deficient' is the correct and cautious verdict rather than a clean bill of health. CITES does not list the species.