Duplicate Cory (Corydoras duplicareus)

One selected quantity supplies one live, unsexed Duplicate Cory in the size shown by the variant selector. This product has approximately 2.5-3 cm and 3-3.5 cm dispatch-size options. Availability and price can change, so use the selector for the live position. One quantity is not a pair or group, and the size band is approximate rather than an exact measurement promise.

The Duplicate Cory is the peaceful, social South American catfish long known in the aquarium trade as Corydoras duplicareus. Its currently accepted scientific name is Hoplisoma duplicareum. It is best planned as a group fish for a mature aquarium with fine smooth sand, reliable filtration, good oxygenation and deliberate bottom feeding.

Duplicate Cory quick facts

Name, identity and natural distribution

Hoplisoma duplicareum is the accepted combination used by the Catalog of Fishes. The older name Corydoras duplicareus remains common in shops, books and searches, so both names are shown here to connect current taxonomy with familiar aquarium usage. The spelling also explains why the fish may be called Duplicate Cory, Duplicareus Cory or, less naturally, Duplicat Cory in supplier lists.

The species is documented from the upper Rio Negro basin in Brazil. That is its wild distribution, not a claim that the individual fish offered here was collected from the wild. Aquarium stock can be captive-bred or pass through commercial supply chains, and the product should not be treated as proof of collection locality unless a specific provenance record is supplied.

A typical Duplicate Cory has a pale body, a dark mask across the eye, a strong dark diagonal or saddle-like band below the dorsal region, and a warm orange-gold area over the head. The exact width and intensity of those markings can vary with age, condition, lighting and individual genetics. Recently transported fish may look paler until they settle, feed and resume normal social behaviour.

Duplicate Corys are often confused with Adolfo's Cory and other upper Rio Negro relatives. A single orange patch or black marking is not enough for a confident identification because related species share parts of the same pattern. Supplier identity, reliable collection or breeding records, accepted names and the full combination of markings are more useful than matching one photograph. See the Adolfo's Cory page when comparing the two trade offerings.

Dispatch size, adult size and sex

The size selected is a dispatch band for a young fish, not its eventual adult length. Standard length measures from the snout to the base of the tail, while total length includes the tail fin. FishBase reports a maximum of 4 cm standard length for this species; aquarium references often describe adults at roughly 5-6.5 cm total length. These figures are not contradictory because they use different measuring conventions.

Growth rate depends on age, feeding, temperature, water quality, genetics and stocking. A smaller arrival should not be force-fed in an attempt to accelerate growth. Consistent water quality and several modest, appropriate feeds are more useful than large meals that leave food decomposing in the substrate.

The fish is sold unsexed. Mature females are often fuller-bodied and can be larger when viewed from above, while mature males may look slimmer, but juvenile sexing is uncertain. Do not order one or two fish on the assumption that they will form a breeding pair. Build the social group first and treat any future sex ratio as unguaranteed.

Group size and aquarium space

Duplicate Corys are social catfish and should not be kept alone. OATA's freshwater catfish guidance recommends at least five smaller Corydoras-type fish together and at least 80 litres for their shoal. Use that as a conservative starting point, not as permission to ignore the aquarium's dimensions or other occupants. A long, open bottom is more useful to these fish than the same volume in a tall, narrow shape.

An 80-litre aquarium can suit a small group only when its footprint, filtration, maintenance and total stocking are appropriate. Choose a larger aquarium for a bigger group, bulky tank mates, territorial bottom-dwellers or a layout that removes much of the usable floor. Every fish must have room to forage and reach food without being crowded away.

A healthy group does not need to move as one tight school all day. Individuals may spread out while feeding, rest near one another and regroup when startled or exploring. The important signs are that they remain visible, forage normally, breathe comfortably and are not persistently isolated or displaced.

Planning the complete group before buying

Because one quantity supplies one fish, work out the full group and aquarium capacity before choosing a quantity. Check the selected dispatch size, then plan for adult total length rather than assuming the fish will remain at the arrival size. A group of five is the sourced minimum social baseline; keeping more can produce confident, interesting behaviour when the aquarium provides the extra bottom area and filtration.

Count every established bottom-dweller in the stocking plan. Plecos, loaches, other cory species and territorial dwarf cichlids may use the same caves, feeding places or floor area even when the middle of the aquarium looks empty. A mixed group of different cory species is not automatically equivalent to a same-species group, because each species benefits from companions it recognises and interacts with naturally.

Introduce the planned group together where practical, provided the filter can support the added bioload. Adding one fish at a time can leave early arrivals without an adequate social group and repeatedly disturb the aquarium. If the group must be built gradually, keep the interval short, monitor water quality after every addition and avoid exceeding the mature filter's capacity.

Before ordering, confirm that the aquarium has:

• at least 80 litres and a useful horizontal footprint for the planned group;
• a mature filter and stable temperature;
• fine smooth sand or another demonstrably gentle, clean substrate;
• open bottom space as well as shaded cover;
• food that sinks in a suitable size; and
• tank mates that cannot swallow, harass or outcompete the arrivals.

Substrate and aquarium layout

Fine smooth sand is the preferred substrate because it allows natural nose-down sifting without sharp edges. Duplicate Corys take mouthfuls of sand, sort edible particles and pass the fine material through their gills. This behaviour is useful to observe, but it does not mean they clean the aquarium or can survive on debris.

If another substrate is used, it should be small, rounded, clean and gentle on the barbels. Sharp material, compacted dirt and accumulated organic waste can all create poor conditions at the bottom. Barbel damage is not caused by one substrate type in every case; water quality, hygiene, chronic irritation and infection also matter.

Provide open feeding and foraging space alongside shaded cover. Smooth wood, broad-leaved plants, low caves and leaf litter can create shelter, while plants around the back and sides help the group feel secure. Keep decorations stable and leave enough clear floor for all fish to feed. Avoid narrow gaps that could trap a startled catfish or collect food beyond reach.

Use reliable biological filtration with gentle-to-moderate circulation and visible surface movement. These catfish can take atmospheric air at the surface, but that natural behaviour is not a substitute for oxygenated water. Repeated frantic surfacing, rapid gill movement or fish gathering in the filter flow should prompt an immediate check of oxygen, temperature and water quality.

Temperature and water conditions

Published species data give a broad temperature range around 22-26°C, pH 6.0-8.0 and hardness extending from soft into moderately hard water. For routine aquarium care, a stable 23-26°C, pH about 6.0-7.2 and roughly 2-15 dGH is a practical target that suits the species while avoiding the extreme edges of the recorded range.

Stability matters more than repeatedly adjusting water to reach a fashionable exact number. Test the source water, understand the conditions used by the retailer, and make changes gradually. The Water Parameter Matcher can help compare this fish with the aquarium you already maintain.

• Cycle and mature the aquarium before the group arrives.
• Keep ammonia and nitrite at zero.
• Control nitrate and organic waste with regular partial water changes.
• Match replacement water closely for temperature and chemistry.
• Vacuum exposed waste without repeatedly disturbing the entire biological bed.
• Maintain oxygenation, especially near the upper end of the temperature range.

Do not chase pH with sudden chemical corrections. A rapid swing within a nominally acceptable range can be more stressful than a stable value toward one side of it. If the household water is very different from the supplier water, use a careful acclimation plan and observe the fish closely during the first week.

Routine maintenance for a bottom-feeding group

Regular maintenance protects the part of the aquarium where these fish spend most of their time. Test water on a consistent schedule, make partial water changes before waste accumulates, and gently remove debris from open feeding areas. Clean only part of the substrate at once when a deep clean is needed so the group keeps familiar cover and the aquarium avoids an abrupt disturbance.

Rinse filter media in removed aquarium water when flow falls or debris builds up; do not replace all mature media at the same time. Check the intake and pre-filter for trapped food, and make sure the return still creates surface movement. A filter can appear to run while clogged media reduces useful circulation and oxygen exchange near the bottom.

Observe the group during maintenance and at feeding time. Comparing normal behaviour from week to week is more useful than reacting to one brief dash or surface breath. A gradual change in appetite, group contact, breathing or barbel condition can reveal a husbandry problem before it becomes severe. Record unusual test results and recent additions so patterns are easier to identify.

When changing temperature or water chemistry for another species, check the Duplicate Cory range first. Community aquariums work only where the animals' needs overlap; one fish should not be kept permanently at the edge of its tolerance to suit another. Stable shared conditions are preferable to repeated adjustments.

Feeding Duplicate Corys properly

Duplicate Corys are omnivorous bottom-feeders. Use a quality sinking catfish tablet, small pellet, wafer or gel food as the staple, then rotate appropriately sized frozen or live foods such as bloodworm, daphnia, cyclops, black mosquito larvae or brine shrimp. Variation supplies different nutrients and encourages natural searching behaviour.

They are not algae eaters in the same sense as a bristlenose pleco, and they must not be expected to live on uneaten flakes. Feed them deliberately after faster mid-water fish have taken their share. Place food in more than one area so subordinate individuals can eat, and watch the whole group rather than assuming food that reaches the bottom reaches every fish.

Offer a portion the group can finish without leaving large amounts trapped under wood or between stones. Young arrivals can benefit from smaller, more frequent meals, while adults usually do well with one or two modest feeds depending on the wider aquarium. Remove obvious leftovers and reduce the next portion if food remains.

A rounded abdomen after feeding can be normal, but persistent wasting, hollow bellies, refusal of food or one fish repeatedly missing meals needs attention. Check competition, food size, water quality and health rather than simply adding more food to the tank.

Temperament and compatible tank mates

This is a peaceful community catfish, but compatibility depends on more than temperament. Tank mates must share the same temperature and water chemistry, remain safe at adult size and allow the cory group to feed. Small peaceful tetras, pencilfish and gentle rasboras can be suitable when the aquarium has enough swimming and bottom space.

Do not mix species only because both are labelled community fish. Compare adult size, water, feeding speed, activity and the space each uses. A calm-looking fish can still outcompete Duplicate Corys at feeding time, while a small territorial fish can make a large part of the bottom unusable.

Adult dwarf shrimp may coexist in a planted aquarium, but no bottom-feeding fish can be guaranteed safe with tiny shrimplets. Snails are usually ignored, although the cory group may investigate food around them. Browse the wider Corydoras and cory-type catfish collection or catfish and pleco collection to compare adult size, group needs and water requirements before mixing bottom-dwellers.

Normal behaviour and health observations

Healthy Duplicate Corys spend much of their time investigating the bottom, pausing under cover and interacting with the group. Brief trips to the surface for air can be normal. New arrivals may hide or look pale for a short period, but they should gradually resume foraging and group contact.

Check barbels, mouth, fins, belly shape, breathing and posture during routine feeding. Warning signs include persistent rapid breathing, clamped fins, sores, white patches, severe barbel erosion, repeated flashing, loss of balance, refusal of food or isolation that continues after the group has settled. These signs do not identify one disease by themselves; test the water first and seek a diagnosis before choosing a treatment.

Good prevention starts with a mature aquarium, stable water, appropriate companions and observation of new fish. A separate mature observation or quarantine setup can reduce the chance of introducing disease, but it must be heated, filtered and maintained properly. Avoid adding medication or salt automatically, and always check product instructions and species suitability.

Arrival and acclimation

Prepare the complete group aquarium before ordering. Confirm that the filter is mature, temperature is stable and ammonia and nitrite are zero. Keep the lights low when the fish arrive and follow the acclimation instructions supplied with the order. Transfer the fish calmly and avoid adding transport water to the aquarium where the supplied instructions advise against it.

Do not offer a large meal immediately. Once the group is settled, provide a small sinking feed and confirm that every fish can reach it. During the first week, watch breathing, posture, colour recovery, barbels, appetite and social contact. Test the water promptly if the group remains distressed.

Livestock cover is governed by the current UK delivery and Live Arrival Guarantee page, including its evidence and contact requirements. The guarantee does not replace the need for a cycled aquarium, compatible water and prompt acclimation.

Breeding context

Duplicate Corys can spawn in aquariums, but one unsexed fish is not a breeding pair and no sex ratio is guaranteed. A mature compatible group, excellent water quality and varied conditioning food are the starting points. Specialist accounts describe spawning after substantial clean water changes, sometimes using slightly cooler replacement water to imitate seasonal cues.

Adults attach adhesive eggs to glass, plants or other surfaces. Eggs and newly hatched fry can be eaten, so breeders often move the eggs or adults to a separate mature setup. Use gentle aeration, protect the biological cycle and feed fry only after they become free-swimming. Tiny live or prepared fry foods must be appropriately sized, and water quality can deteriorate quickly when food is overused.

Breeding results vary with the fish, sex ratio, condition and environment. Treat any trigger method as experience-based guidance, not a guaranteed formula. The welfare and social needs of the main group remain more important than trying to force a spawn.

How the Duplicate Cory compares with similar fish

Do not choose between Duplicate Cory, Panda Cory, Bronze Cory or Adolfo's Cory from colour alone. Compare adult size, temperature, group size, source reliability and the aquarium's footprint. When maintaining more than one cory species, each species still needs an appropriate social group; a mixed collection is not automatically a substitute for same-species companions.

Gallery note

The four gallery images are illustrations that broadly represent the supplied trade identity. They are not photographs of the exact fish dispatched, and the two-fish scene does not mean that one quantity includes two fish. Natural colour, markings, body shape and apparent size can vary between individuals and under different aquarium lighting.

Sources and further reading

The name, distribution and biological ranges above are cross-checked against taxonomic and species databases, while the aquarium guidance uses established UK trade and specialist husbandry references. These sources provide context rather than a promise that every individual will behave or grow identically.

• Eschmeyer's Catalog of Fishes: Hoplisoma duplicareum - accepted name, synonymy and distribution.
• FishBase species summary - standard length and reported environmental ranges.
• OATA freshwater catfish care sheet - group, aquarium, feeding and maintenance guidance.
• Fishkeeper Duplicate Cory profile - specialist aquarium identification and husbandry context.
• Corydoras World breeding account - experience-based spawning observations.