Duplicate Cory (Corydoras duplicareus)

Identify the Duplicate Cory and plan for its adult length

The Duplicate Cory is a peaceful, gregarious freshwater catfish from the upper Negro River basin in South America. It belongs to Callichthyidae, the family of callichthyid armoured catfishes, and spends its aquarium life close to the bottom. It suits a keeper prepared to maintain a social group, provide deliberate sinking meals and keep a clean substrate in a mature filtered aquarium.

FishBase records a maximum of 4 cm standard length for this fish and now lists it as Hoplisoma duplicareum. The familiar aquarium name remains Corydoras duplicareus. Standard length runs from the snout to the base of the tail, so it excludes the tail fin.

A separate Seriously Fish species profile gives a planning length of 5 cm standard length. Use the 5 cm standard-length figure when planning aquarium space. Aquarium space, group planning and feeding access should accommodate this figure instead of being based on the dispatch size.

Decide whether this fish fits your aquarium

This fish suits an aquarist prepared to maintain a social group, keep the substrate clean and place food where every individual can reach it. Its peaceful temperament does not remove the need to check the complete community: competition at the bottom can matter even when there is no aggression.

Choose the dispatch size and quantity as separate decisions

One purchase supplies one Duplicate Cory in the size selected. The dispatch sizes are 2.5–3 cm and 3–3.5 cm. Use the live size selector to choose between the sizes shown.

The size you select is the size supplied, not the adult size. A 2.5–3 cm fish therefore needs an aquarium planned around the 5 cm standard-length reference, its social group and the space occupied by every other fish. The larger dispatch band does not represent a different adult form or a different care category.

Quantity and size perform different jobs in the plan. The selected size determines the dispatch band; the purchase quantity determines how many individual fish are ordered. If the aquarium has no Duplicate Cory group, first decide whether it can support at least 4–6 individuals. If companions are already present, count their adult space and feeding demands before setting the quantity.

Sex is guaranteed only when the selected option explicitly states male or female. This Duplicate Cory listing has no sex-guaranteed option.

Check the offer against the aquarium plan

• Select the required dispatch-size band.
• Remember that each purchase represents one animal.
• Base the social plan on at least 4–6 individuals, not on a presumed pair.
• Allow for the larger 5 cm standard-length planning reference.
• Confirm that the aquarium can provide shared water conditions and enough clean bottom space.

Some gallery images have been digitally enhanced to improve image quality. They show the listed type of animal rather than guaranteeing the exact markings of the individual supplied, so natural colour and pattern can vary.

Apparent sex, body size or colour in an image does not alter the offer. Use the live size selector, remember that each purchase supplies one fish, and confirm that the aquarium can support a complete social group.

Plan aquarium space for the whole social group

Keep the Duplicate Cory in a group. The species profile says it should be maintained in a group of at least 4–6 individuals, while OATA recommends at least five for Corydoras generally. A plan for five meets OATA’s baseline and sits within the species profile’s stated group range; six provides another supported starting point when the aquarium has the extra floor space and filtration capacity.

OATA’s freshwater-catfish sheet gives broad group guidance of an aquarium of at least 80 litres for a shoal of smaller Corydoras or a smaller pleco. Use 80 litres as the starting volume for a small group, then increase space where the footprint, décor, established population or larger group reduces usable bottom area.

Work through volume and footprint together

Volume helps water conditions remain stable, but litres alone do not describe the shape of the aquarium. A tall layout can contain the baseline volume while offering less bottom room than a longer design. Judge the clear floor after wood, plants, pots and other cover have been positioned.

Plan each fish at its adult reference length, even when all selected fish arrive at 2.5–3 cm. For example, five fish planned at 5 cm standard length represent a group whose eventual use of the bottom will be very different from five newly dispatched fish. Use this comparison alongside filtration, other inhabitants and the actual layout when deciding whether the aquarium has enough space.

Additions should not exceed the capacity of the mature biological filter. If the aquarium population must be increased gradually, test after each addition and preserve the supported social minimum rather than leaving one fish alone for an extended period.

Build a secure bottom layout with clean fine sand

Fine sand is the preferred substrate. Rounded gravel is an acceptable alternative when it is kept scrupulously clean, but sand provides the straightforward choice for a fish that forages along the bottom. Whatever material is chosen, remove trapped food and solid waste before it accumulates around resting and feeding places.

Arrange open foraging areas beside cover. Driftwood branches and dried leaf litter are useful additions, while plants and other secure décor can create shaded resting places. Cover helps the group feel secure without taking away every clear area where sinking food can be found.

Lay out the aquarium in practical zones

• Open feeding zone: keep a clean patch where portions can be seen and monitored.
• Covered zone: provide shelter using stable wood, plants or suitable ornaments.
• Movement route: leave an unobstructed path between feeding space and cover.
• Service area: keep the filter intake and accessible substrate clear enough to inspect.

Dried leaves decompose over time and can encourage colonies of microorganisms. The species profile describes those microorganisms as a valuable secondary food source for fry, while tannins and other chemicals released by the leaves are thought beneficial and can help imitate natural conditions. Leaves remain décor and habitat enrichment rather than a replacement for deliberate meals.

Keep every decoration stable. Bottom-foraging fish repeatedly move around the bases of wood and plants, so a layout should not depend on loose pieces balancing against one another. Avoid creating inaccessible pockets where sinking food can disappear and decay.

Check the substrate during each maintenance session. If food repeatedly gathers in one corner, alter the feeding position or circulation rather than allowing that point to become a permanent waste trap. When rounded gravel is used, inspect between the grains because debris can settle below the visible surface.

A useful finished layout lets you answer three questions clearly: can all group members reach food, can they move between cover and open floor, and can waste be removed without dismantling the aquarium? If any answer is no, adjust the décor before the fish are introduced.

Set stable water conditions before adding the group

Keep the aquarium at 22–26°C, pH 6.0–7.0 and 2–5 dGH. These values are the overlap between the Seriously Fish aquarium range of 20–26°C, pH 4.0–7.0 and 1–5 dGH and FishBase’s recorded environmental range of 22–26°C, pH 6.0–8.0 and 2–25 dH.

Measure the aquarium rather than choosing values by assumption. Our water chemistry guide explains the values to test, and the Water Parameter Matcher can compare measured aquarium conditions with the stated guidance.

Use one consistent decision sequence

1. Measure temperature, pH and general hardness in the prepared aquarium.
2. Compare all three readings with 22–26°C, pH 6.0–7.0 and 2–5 dGH.
3. Confirm ammonia and nitrite are both zero mg per litre.
4. Keep nitrate no more than 20 mg per litre above its normal tap-water level.
5. Correct the aquarium gradually before adding fish rather than making repeated abrupt changes afterwards.

The group-level OATA values are zero mg per litre ammonia, zero mg per litre nitrite and nitrate no more than 20 mg per litre above normal tap-water levels. These waste readings are operating limits for aquarium maintenance, not optional targets to approach.

Stability matters because every correction affects the whole group. Test replacement water as well as aquarium water when the two differ noticeably. Matching temperature and avoiding abrupt chemistry changes makes routine maintenance more predictable.

Maintain the biological filter and remove waste every week

A working filter is essential. The RSPCA’s aquarium guidance explains that fish release toxic ammonia and that beneficial bacteria in a biological filter convert it first to nitrite, which is also toxic, and then to safer nitrate. The filter must therefore be established before the Duplicate Cory group is introduced.

The species profile says filtration can be gentle, with an air-powered sponge-style unit normally adequate, although some water movement is acceptable. Choose filtration that processes the aquarium’s total waste while leaving the bottom group able to forage and rest normally.

Follow a repeatable weekly routine

• Test ammonia and nitrite at least once each week and keep both at zero mg per litre.
• Check nitrate against the limit of no more than 20 mg per litre above normal tap water.
• Change 25% of the water at least once every week.
• Treat replacement tap water with conditioner to remove chlorine or chloramine.
• Remove solid waste from exposed substrate with a siphon.
• Check the filter for blockages and confirm that flow remains effective.

Do not rinse biological filter media under the tap. Chlorine or chloramine may kill the established bacteria. If cleaning is needed, rinse the media lightly in aquarium water removed during the partial water change. This protects more of the bacterial population while clearing debris.

A clogged filter may continue making noise while moving less water. Look at the return flow rather than relying on sound alone, and inspect the intake for trapped leaves or food. Clean only as much as needed to restore function; replacing all established media at once removes the bacteria that process waste.

Use the water change to inspect feeding areas. Siphon visible debris without turning every session into a complete rearrangement. If one zone remains dirty between changes, reduce the portion landing there, improve access for cleaning or adjust the layout.

Record unusual ammonia, nitrite or nitrate readings and note recent fish additions or feeding changes. A simple sequence of dated results makes it easier to see whether the filter has recovered before any further increase in stocking.

Feed every Duplicate Cory rather than relying on leftovers

Duplicate Corys are foraging omnivores. Offer quality sinking dried food as the regular meal and rotate suitably small live or frozen foods such as chironomid larvae, commonly called bloodworm, or Tubifex. Freeze-dried bloodworm can also form part of the varied diet described for this group.

These catfish must not be expected to survive on leftovers from other aquarium inhabitants or be relied upon to clean the aquarium. Food reaching the bottom by accident does not show that every member of the group has eaten. Place a deliberate sinking portion where the fish can find it and remain present long enough to observe the whole group.

Use a simple once-daily feeding check

1. Offer only what the fish can eat within a few minutes, once a day.
2. Distribute food across more than one accessible point when one fish blocks the first position.
3. Watch for each group member to approach and feed.
4. Remove uneaten food rather than leaving it to break down.
5. Reduce the next portion if food remains after the feeding period.

The once-daily schedule comes from OATA’s general catfish guidance. The species profile supplies the more precise food choices: sinking dried products plus small live and frozen varieties. Together they provide a workable routine without treating scavenging as nutrition.

Variation means changing suitable foods over time, not giving a large mixed portion at every meal. Keep each feed modest and use observation to judge whether the whole group is maintaining interest in food.

Leaf-litter microorganisms may provide secondary food for fry, but adult aquarium care still requires deliberate sinking food. A clean-looking bottom is not evidence that the group has received a complete meal.

Prepare the aquarium and introduce livestock gradually

Complete the aquarium before the group arrives. The filter should be mature, the temperature should sit within 22–26°C, and tests should show zero mg per litre ammonia and zero mg per litre nitrite. Arrange the fine substrate, open feeding area and cover before fish are added so their first days are not interrupted by a major rebuild.

If this is your first setup, follow our first tropical aquarium guide to prepare and mature the system before livestock is introduced. Maturation allows the filter’s beneficial bacteria to establish before feeding and fish waste increase the biological load.

Complete the pre-introduction check

• Measure temperature, pH and hardness against the chosen care range.
• Confirm ammonia and nitrite are zero mg per litre.
• Check that filter flow has not fallen because of a blockage.
• Make sure at least 80 litres and a useful bottom footprint are assigned to the small group plan.
• Place suitable sinking food within easy reach.
• Confirm that every established inhabitant passes the compatibility screen.

Increase aquarium stocking slowly because the beneficial bacterial population must grow as fish numbers and feeding rise. Adding too many fish too quickly can produce new tank syndrome, in which the filter bacteria cannot process the additional waste and ammonia or nitrite rises to harmful levels.

Social need and filter capacity must be considered together. Do not use slow stocking as a reason to keep one Duplicate Cory alone indefinitely. Instead, prepare enough mature capacity for the supported group, or delay the introduction until that capacity exists.

Follow the arrival steps in order

1. Have someone present to receive the parcel.
2. Start filming before opening it, showing the sealed parcel and outer box.
3. Continue filming in one take as the parcel is opened, with the fish still inside the sealed bag.
4. Float the bag for 20–30 minutes before releasing the fish.
5. Never pour the bag water into the aquarium.

Keep the video and order number for any Live Arrival Guarantee claim. The full terms are on the delivery and Live Arrival Guarantee policy.

Watch the first week closely

Check water after the addition and observe swimming, breathing, colour, feeding and group contact. Test promptly when behaviour changes or appetite falls. Keep the feeding portion modest while confirming that the filter continues to hold ammonia and nitrite at zero.

Respond early to changes in behaviour, breathing or feeding

Learn the group’s ordinary pattern during feeding and quiet periods. OATA recommends watching swimming behaviour, colour, temperament, breathing, appearance, body condition and food intake. A change matters most when it persists or appears alongside another change.

Use observation to choose the next action

Sitting on the bottom is included in OATA’s general warning list because it can represent a change in some fish. For a demersal catfish, location alone is less useful than a departure from its usual posture, movement and feeding. Compare the individual with its established pattern and the rest of the group.

Begin with measured conditions rather than guessing at a disease. Ammonia and nitrite should remain at zero mg per litre, and the filter should maintain normal flow. If a reading has changed, protect water quality and seek appropriate fish-health advice rather than choosing a treatment from appearance alone.

Inspect the whole group during the daily meal. One fish repeatedly failing to reach food may indicate competition even when the aquarium appears peaceful. Add a feeding point, watch again and check whether bottom space is being blocked by another inhabitant.

Continue the 25% partial water change at least once a week and maintain the testing routine when everything appears normal. Consistent records create the baseline that makes a genuine change easier to recognise.

Screen every community companion before mixing species

The Duplicate Cory is described as peaceful and gregarious, and OATA places Corydoras among the catfish commonly kept in community aquariums. That describes the fish’s broad temperament, but each proposed pairing still needs a practical assessment.

Begin with water overlap. A companion should be maintainable within 22–26°C, pH 6.0–7.0 and 2–5 dGH without forcing either animal to live at an unsuitable value. Compare the planned stable setting rather than accepting a tiny overlap at the edge of two ranges.

Apply four checks in order

1. Adult size: judge every species at its adult planning size, not its dispatch size.
2. Water: require a stable overlap in temperature, pH and hardness.
3. Feeding: make sure sinking meals can reach every Duplicate Cory.
4. Space: preserve enough bottom room for the full group, cover and open feeding zones.

The word “community” is not a complete compatibility decision. Two peaceful fish can still require different water, and two bottom-oriented species can compete for the same feeding places without obvious aggression.

Assess each proposed pairing by comparing adult size, water needs, feeding behaviour and aquarium dimensions before the animals are mixed. Base the stocking and compatibility assessment on the aquarium volume and footprint, measured water values, filter status, décor plan and exact species already present.

Browse the catfish and pleco collection to compare identity and care requirements, but assess each candidate separately rather than assuming all catfish share this fish’s size or temperament.

Protect the group’s access to food, cover and bottom space

Compatibility continues after the fish are introduced. A combination that shares water values can still fail if one inhabitant controls the bottom, reaches every sinking meal first or leaves the Duplicate Cory group without usable cover.

Observe at feeding time because that is when hidden competition becomes visible. Every group member should have a route to food and enough time to eat. If one area is crowded, split the portion between separate open zones rather than simply adding more food to the same place.

Separate social confidence from crowding

• A group of at least 4–6 meets the species profile’s social direction.
• At least 80 litres is broad starting guidance for a shoal of smaller Corydoras.
• A larger group needs additional usable floor area and biological capacity.
• Other bottom inhabitants count against the same feeding and shelter space.
• More food does not fix a layout in which one fish blocks access.

Cover should create several usable resting choices without consuming the entire floor. When all shelter is concentrated beneath one piece of wood, another inhabitant can make that area difficult to use. Spread secure cover through the layout and retain clear routes between it and the feeding zones.

Reassess the community whenever fish are added or the décor is changed. A new ornament can remove feeding room just as effectively as another bottom-dweller, while a new fish increases both competition and filter load.

The most reliable community plan combines peaceful behaviour with measurable water overlap, deliberate feeding and sufficient space. Continue daily observation and weekly testing after the initial introduction rather than treating compatibility as a one-time decision.

Answer the key questions before choosing this fish

How big does the Duplicate Cory get?

The Duplicate Cory reaches 4 cm standard length according to FishBase; Seriously Fish gives a separate 5 cm standard-length planning reference.

What size aquarium does Corydoras duplicareus need?

Use an aquarium of at least 80 litres for a small group. This is OATA’s broad guidance for a shoal of smaller Corydoras, so also assess the footprint, décor, filtration and other inhabitants.

How many Duplicate Corys should I keep together?

Keep at least 4–6 Duplicate Corys together, as directed by the Seriously Fish species profile; OATA recommends at least five for Corydoras generally.

Does Corydoras duplicareus suit beginners?

Corydoras duplicareus suits a keeper prepared to maintain a mature filtered aquarium, a group of at least 4–6, stable water, clean substrate and deliberate feeding.

What does the Duplicate Cory eat?

Feed the Duplicate Cory quality sinking dried food with suitably small live, frozen or freeze-dried foods. OATA’s catfish guidance says to feed once a day, offering only what can be eaten within a few minutes.

What temperature and pH does this fish need?

Keep it at 22–26°C, pH 6.0–7.0 and 2–5 dGH, the overlap between FishBase’s environmental values and the Seriously Fish aquarium range; ammonia and nitrite must remain at zero mg per litre.

Is it aggressive or likely to nip fins?

This fish is described as peaceful and gregarious. Screen each community combination for adult size, shared water, feeding access and bottom space rather than relying on temperament alone.

Which kinds of animals can Corydoras duplicareus live with?

It can be considered for a peaceful community aquarium when every companion shares its water range and allows the group enough bottom space, cover and access to sinking food.

How does the Duplicate Cory arrive alive in the UK?

Start filming before any floating, showing the sealed parcel and outer box, then continue in one take as it is opened with the fish still in the sealed bag. Someone must be present to receive it; float the bag for 20–30 minutes, then release the fish without pouring the bag water into the aquarium.

Check the identity and husbandry references

• FishBase: Hoplisoma duplicareum — accepted name, synonym, family, distribution, environmental values and maximum recorded standard length.
• Seriously Fish: Corydoras duplicareus — aquarium water range, substrate, cover, filtration, diet, social group and reproduction notes.
• OATA freshwater catfish guidance — UK group advice for aquarium volume, water quality, feeding, maintenance, introduction and observation.
• RSPCA aquarium environment guidance — biological filtration and the aquarium nitrogen cycle.