Two-Tone Concolour Cory - Hoplisoma sp. aff. "concolor Rio Tomo" Fish Profile & Care Guide
Introduction
The Two-Tone Concolor Cory Catfish (Hoplisoma sp. aff. concolor “Rio Tomo”), often traded under the code CW217, is an undescribed local form closely related to the Slate Cory, Hoplisoma concolor. In older books and in much of the hobby it would have been treated as a Corydoras type catfish, and you will still hear it called a “cory” today. Taxonomically, it is now placed in the genus Hoplisoma rather than Corydoras, following revisions to the Corydoradinae group.
It is prized for a richer, more contrasting two-tone look than typical H. concolor, while keeping the same gentle, busy, always-foraging character that makes cory catfish such dependable community favourites.
Like other Hoplisoma corys, the Two-Tone Concolor Cory Catfish is highly social and settles best when kept in a proper group of its own kind. In numbers, they become noticeably bolder, spend more time out in the open, and show more natural behaviours such as coordinated bottom patrols and relaxed, confident feeding. Kept singly or in very small groups, they can become withdrawn and skittish, and are more likely to be outcompeted at mealtimes.
Two-Tone Concolor Corys are peaceful and should be paired with calm, non-aggressive community fish that will not harass bottom dwellers. Suitable companions include gentle small to medium characins, rasboras, peaceful livebearers, and mild-mannered dwarf cichlids, along with other non-bullying catfish. Avoid large, boisterous cichlids and anything known for fin nipping or persistent food-guarding, as this fish prefers to feed unhurriedly across the substrate and can be stressed by constant pressure.
Set the tank up around safe foraging and low stress. A soft, smooth sand or similarly gentle substrate is strongly recommended because these fish constantly root and sift with delicate barbels. Provide broken lines of sight and plenty of shade using plants, driftwood, and leaf litter style cover so they feel secure enough to stay active throughout the day. They do best in a mature, well-maintained aquarium with consistently clean water, good oxygenation, and steady filtration that keeps things fresh without blasting the bottom.
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Sexual Dimorphism
Sexual dimorphism in Two-Tone Concolor Corydoras follows the usual cory pattern and is easiest to judge once the fish are mature. Females typically grow a little larger and look noticeably broader-bodied, especially when viewed from above. When in breeding condition, they develop a fuller, rounder belly, giving them a more “pear-shaped” outline compared with males. Males are generally slimmer and more streamlined, and they are the ones most likely to show fin extensions. In CW217 specifically, breeders and import notes commonly mention longer, more pointed pelvic (belly) fins in males, while females’ pelvic fins are shorter and more rounded (used to help cradle eggs during spawning). Some males also develop a more extended dorsal fin, but fin length can vary between individuals, so it is best used as a supporting clue rather than the only deciding feature.
Sexual differences follow the usual cory catfish pattern and are easiest to judge once the fish are mature. Females typically grow a little larger and look broader-bodied, especially when viewed from above. When in breeding condition, they develop a fuller, rounder belly, giving a more “pear-shaped” outline compared with males. Males are usually slimmer and more streamlined.
Fin shape can provide supporting clues, but it varies between individuals. Some keepers report males showing slightly longer or more pointed pelvic fins in CW217-type fish, while females’ pelvic fins can appear shorter and rounder (useful for cradling eggs during spawning). Treat fin length as a secondary hint rather than a single deciding feature.
Quick Facts
| Scientific Name | Hoplisoma sp. aff. "concolor Rio Tomo" |
|---|---|
| Year Described | 2025 |
| Kingdom | Animalia |
| Classification | Actinopterygii |
| Order | Siluriformes |
| Family | Callichthyidae |
| Genus | Corydoras |
| Origins | Colombia |
| Approx Max Size | 6.5 cm |
| Temperament | Peaceful |
| Aquarium Level | Bottom |
| Difficulty | Beginner - Intermediate |
| Shoaling | Yes |
| Best kept as | Groups 6+ |
| Diet & Feeding | Omnivore |
| Reproduction | Egg Depositor |
| Average Lifespan | Up to 8 Years |
Water Parameters
| Water Type | Freshwater |
|---|---|
| pH | 6.0 - 7.5 |
| GH | 2 - 10 |
| KH | 0 - 2 |
| TDS | 50 - 150 |
| ℉ | 71 - 77 |
|---|---|
| ℃ | 22 - 25 |
Natural Habitat
The Two-Tone Concolor Cory is widely reported in the hobby as a very local fish from eastern Colombia within the Orinoco drainage. Trade information states it is collected from a small clearwater tributary connected to the Río Tomo, within the Orinoco Basin. Collectors reportedly refer to this tributary as Caño Negro, and the water at the collection site has been described as crystal clear. The same source notes that CW217 is the only armoured catfish recorded from Caño Negro, and that H. concolor is not recorded there, which is one reason the form is treated as distinct in the hobby as an “aff.” locality variant even though it closely resembles H. concolor.
The Río Tomo itself is described as an Orinoco tributary flowing through the open plains region of eastern Colombia, and is sometimes reported at around 650 km in length. This fits the general Llanos and clearwater tributary context hobbyists associate with the fish, where seasonal changes can strongly influence water level, flow, and access to flooded margins.
Breeding
Breeding reports for Two-Tone Concolor Corys are still relatively scarce, largely because the fish has tended to appear in the trade in small numbers and is not yet widely established. Most keepers therefore approach it using the well-known breeding patterns seen across Hoplisoma and other corydoras-type catfish, where courtship and egg-laying behaviour is often broadly similar.
When they are ready to spawn, you will typically see a sharp increase in activity: zooming, group chasing, and repeated pairing attempts. Spawning commonly centres around the classic “T-position”, where the female presses in close to the male. After this, she forms a small clutch of eggs held between her pelvic fins before placing them one by one on firm surfaces. Eggs are often stuck to aquarium glass, plant leaves, hard decor, or areas with good flow and oxygenation, depending on the setup and the fish’s preferences.
To improve the chance of eggs, breeders usually focus on conditioning a group with generous, high-quality foods and then imitating a “fresh influx” event. This is commonly done with substantial water changes using clean, slightly cooler water and strong aeration. Some hobbyists also report improved results when these changes coincide with weather fronts and shifts in pressure, which may mirror natural seasonal cues.
Once eggs appear, the main challenge is protection and hygiene. Adults may eat eggs if given the opportunity, so breeders often remove the adults or move the eggs to a separate rearing container with gentle circulation. Clean water, steady oxygenation, and low-stress lighting help reduce losses, while first foods for fry must be very small until they can manage larger live foods.
Diet & Feeding
In the wild, Two-Tone Concolor Corys are best thought of as bottom-sifting micro-predators rather than “clean-up crew”. They take mouthfuls of fine substrate and filter out edible items such as small worms, tiny crustaceans, insect larvae, and other microorganisms. In the aquarium you will see the same behaviour, with fish constantly nosing through the substrate and picking at biofilm on plants and wood.
In captivity they do best on a varied, sinking diet that reliably reaches the bottom. Quality sinking tablets or micro-pellets make a solid staple, supported with frozen or live foods such as bloodworm, daphnia, and other small meaty options that match their natural feeding style. Feed them intentionally rather than relying on leftovers from mid-water fish.
Practical feeding is mostly about access and cleanliness. Spread food across a couple of spots so the whole group can eat without crowding, and so shyer fish do not miss out. Keep portions sensible and remove uneaten food, because this species spends its life on the substrate and is among the first to suffer if the bottom becomes dirty or oxygen-poor from decaying waste.
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Published: 05 Jan 2026
Last Updated: 06 Jan 2026