Imitator Catfish (Brachyrhamdia imitator)

Choose a catfish that hides in plain sight among Corydoras

The Imitator Catfish (Brachyrhamdia imitator) is a small South American catfish that has made a career of looking like something else. Planet Catfish explains that its name alludes to the fact that it shares, identically, the colour pattern of the spotted cory Corydoras melanistius, known today as Hoplisoma melanistium. In the wild it swims with those Corydoras, and in the aquarium the Imitator Catfish is at its best in the same company.

It comes from the Caura River basin in the Orinoco drainage of Venezuela, according to FishBase, and was described by George Myers in 1927 from the Caño de Quiribana near Caicara. It is the type species of its genus. Seriously Fish describes its close relatives as rarely seen in the trade, usually arriving mixed in with shipments of other fish, so it is a catfish for keepers who enjoy something unusual.

Check the names on the label

The genus name joins the Greek for "short" with Nhamdia or Jamdia, a Brazilian local name for these catfish. It belongs to the Heptapteridae, the three-barbeled catfishes, the same family as the Graceful Pimelodella. Seriously Fish notes that the family was once treated as part of the Pimelodidae but molecular studies support it as separate.

Tell a False Cory from a real Corydoras

At a glance it passes for a cory. Planet Catfish says that anything more than a quick glance reveals the long barbels and naked flanks, and Seriously Fish puts the difference the same way: Brachyrhamdia have significantly longer barbels than Corydoras and no scute-like plates on the body.

Compare three features

Why it copies a cory is still debated. Seriously Fish and ScotCat describe two ideas: that it gains protection from predators wary of the Corydoras' locking spines, or that it shoals with them to take the food they dig up, and possibly their eggs. Seriously Fish adds that several Brachyrhamdia species copy the Corydoras they live with throughout their lives.

Know exactly what you receive

One purchase supplies one live Imitator Catfish at the size currently available ("Standard"). Sex is not chosen or guaranteed; Planet Catfish lists sexing as unknown, and Seriously Fish says that in the genus mature females are noticeably fuller in the body.

The photographs show the type of fish, not the individual you will receive. Because the pattern copies a spotted cory with a black stripe through the eye, expect a pale body with dark markings; the exact layout differs between fish.

Plan the group before you order

• One Imitator Catfish with a Corydoras group: the simplest, most natural set-up.
• Two or more: Seriously Fish says Brachyrhamdia are not especially gregarious with their own kind, but more than one can usually be kept if the tank is not too small; Planet Catfish says it is peaceful with its own species.
• The Corydoras: plan a group of similarly marked corys, ideally with a dark band through the eye; see the tank mates section below.

Before you order, read our delivery and Live Arrival Guarantee information and have the aquarium ready and matured.

Plan the aquarium around a 7–9 cm adult

Sizes depend on how the fish is measured. FishBase and Planet Catfish give 5.4 cm standard length, which stops at the base of the tail. ScotCat gives 7 cm and Welsfans about 9 cm total length, including the tail. Plan for a slim, fast fish of around 7–9 cm in total.

ScotCat recommends a tank of 60 cm or more, Welsfans 80 cm, and Seriously Fish gives an 80 × 30 cm base for the related B. rambarrani. Because the Imitator Catfish should share its floor with a group of Corydoras, we recommend at least 80 × 30 cm.

Run a three-step space check

1. Measure the base: at least 80 × 30 cm.
2. Count the floor fish: the Imitator Catfish and every Corydoras share the same sand, so a larger group of corys needs a larger base.
3. Work out the volume: our tank volume calculator turns your measurements into litres for the filter and heater.

Position the tank away from radiators, windows and draughts, as OATA's catfish care sheet recommends, and fit a lid: a fast, startled fish can jump.

Lay open sand bordered by quick retreats

Planet Catfish says an open stretch of substrate, where it can mix with its own kind or with Corydoras, is necessary to see it at its best. Floating plants diffuse the light and give the fish more confidence in the open, and the open area should be bordered by hiding places with easy entry and exit for this fast swimmer. ScotCat suggests alternating sand and gravel with a planted area.

Divide the floor by function

Use smooth sand or fine, rounded gravel. OATA notes that catfish barbels are sensitive and need a soft bottom, and Seriously Fish warns that the related B. rambarrani does not tolerate a build-up of organic waste, so keep the substrate clean.

Keep the water cool-tropical and clean

The published temperatures disagree. Planet Catfish gives 20–24°C, FishBase and ScotCat 21–25°C, and Welsfans 25–29°C. We suggest 22–24°C, which sits inside the first three and also suits the spotted cory it copies: Seriously Fish gives 22–26°C for Hoplisoma melanistium. Planet Catfish and FishBase agree on pH 6.0–7.5 and hardness up to 18 dGH.

Match your tap water to the range

The ammonia, nitrite and nitrate limits come from OATA's catfish guidance. Treat every water change with a conditioner to remove chlorine or chloramine. Compare your own readings with our water matcher, and see our water chemistry guide for what each one means.

Filter gently and change water every week

A small catfish living on the sand needs clean, well-oxygenated water without a strong current. Seriously Fish suggests a turnover of four to five times the tank volume an hour for an 80 × 30 cm Brachyrhamdia tank, which it puts at about 290–360 litres an hour. Point the outlet to ripple the surface rather than blast the sand.

Follow a weekly routine

1. Test ammonia, nitrite and nitrate.
2. Change about 25% of the water; OATA gives this as the weekly figure.
3. Siphon the open sand gently, especially where food collects.
4. Remove leaves that have broken down.
5. Rinse filter media only in water taken from the tank.

OATA warns that adding fish too quickly causes "new tank syndrome", because the filter bacteria need time to catch up. Add the Corydoras group and the Imitator Catfish in stages, testing between each.

Feed small meaty meals without overdoing it

Wild Brachyrhamdia feed mostly on small invertebrates living on the bottom, Seriously Fish says, and Welsfans lists ostracods, insect larvae and seeds from stomach contents. ScotCat calls it an easy feeder on tablets, pellets, frozen and live foods such as bloodworm, and insect larvae. Planet Catfish adds a warning: it will eat most foods to the point of bursting, so do not overfeed, especially with foods that swell after eating.

Build one measured meal

• Staple: a small sinking pellet or tablet, shared with the Corydoras.
• Meaty food: thawed frozen bloodworm, Daphnia or brine shrimp several times a week, as Seriously Fish recommends for the genus.
• Live food: keep it for settling new fish or conditioning, as Planet Catfish suggests.
• Soak dry food: soak pellets that expand before feeding.
• Portion: only what is eaten within a few minutes, once a day, as OATA advises.

Introduce it calmly to a mature aquarium

Add it only to a mature, filtered aquarium with zero ammonia and nitrite. OATA recommends acclimatising with the lights off: float the sealed bag for about 10 minutes, add small amounts of aquarium water to the bag over up to 20 minutes, then release the fish with as little bag water as possible. Our guide on how to acclimatise new fish covers each step.

Use a first-week checkpoint plan

Choose Corydoras and mid-water fish it cannot eat

Planet Catfish describes it as peaceful with its own species and with Corydoras, but says it will eat small tetras and young fish; fish larger than about 2.5 cm (1 inch) are too big to eat and are not otherwise bothered. ScotCat suggests a species tank, or one with Corydoras and larger characins or anabantoids in the upper half, warning that it can be predatory with small species such as neon tetras. Planet Catfish names tetras, rasboras and rainbowfish as good companions, as long as they are large enough.

Screen each companion

ScotCat reports that it does better with Corydoras that have a black eye stripe, such as Hoplisoma melanistium, than with plain species such as the bronze cory, which tend to be nipped and driven out of the group. Seriously Fish gives the same advice for a related species: keep it with similarly patterned Corydoras and no other bottom-dwelling fish. Read our Corydoras care guide, browse all Corydoras catfish and tetras, and check the final mix with our tank mates tool. For other unusual bottom fish, see our catfish and plecos and South American catfish.

Watch for problems early

OATA describes a healthy fish as having clear eyes, undamaged fins, no ulcers or bumps, normal swimming and steady breathing. With a fish that copies its tank mates, it is worth counting both species daily for the first few weeks.

Pair each sign with an action

Understand what is known about breeding

Planet Catfish records one failed spawning, published in the Catfish Association of Great Britain journal in April 1986. A group began to spawn when their Corydoras melanistius tank mates did; the corys laid their eggs on the glass, while the Imitator Catfish stuck theirs to the leaves of large Vallisneria plants. The water was soft and slightly acidic, and the eggs did not develop. Seriously Fish mentions the same observation. Nothing more is known, so any spawning in your tank is worth writing up.

Answer Imitator Catfish buying questions

What is an Imitator Catfish?

It is Brachyrhamdia imitator, a small three-barbeled catfish (family Heptapteridae) from the Caura River basin in the Orinoco drainage of Venezuela. It is also sold as the False Cory or False Corydoras because its colour pattern copies a Corydoras, the spotted cory Corydoras melanistius (now Hoplisoma melanistium).

How can I tell it from a real Corydoras?

Look at the barbels and the sides of the body. Corydoras have short barbels and bony, scute-like plates along the body. The Imitator Catfish has much longer barbels and smooth, naked skin with no plates, and it is a fast swimmer.

How big does Brachyrhamdia imitator grow?

FishBase and Planet Catfish give 5.4 cm standard length, measured without the tail. ScotCat gives 7 cm and Welsfans about 9 cm total length, so expect an adult of roughly 7–9 cm including the tail.

What size aquarium does it need?

ScotCat recommends a tank of 60 cm or more; Welsfans suggests 80 cm. Because it is best kept with a group of Corydoras, we recommend a base of at least 80 × 30 cm.

What water conditions does it need?

Planet Catfish gives 20–24°C, pH 6.0–7.5 and hardness up to 18 dGH; FishBase and ScotCat give 21–25°C. Welsfans gives a much warmer 25–29°C. We suggest 22–24°C, pH 6.0–7.5 and soft to medium water.

Is it safe with small fish?

Not with very small ones. Planet Catfish says it will eat small tetras and young fish, though fish over about 2.5 cm (1 inch) are left alone. ScotCat warns specifically about neon tetras, so choose larger tetras and other mid-water fish.

Which Corydoras should I keep with it?

Similarly marked Corydoras. ScotCat reports that it does better with Corydoras that have a black stripe through the eye, such as Hoplisoma melanistium, while plain species such as the bronze cory tend to be nipped and driven out of the group.

Has it been bred in aquariums?

Only partly. Planet Catfish records a spawning, reported to the Catfish Association of Great Britain in 1986, in which the fish laid eggs on Vallisneria leaves when their Corydoras melanistius tank mates spawned, but the eggs did not develop.

How many fish come with one purchase?

One live fish of the standard size currently available. Sex is not chosen or guaranteed.

Consult the care references

• Planet Catfish: Brachyrhamdia imitator — names, size, distribution, water range, feeding, furniture, compatibility and a recorded spawning.
• FishBase: Brachyrhamdia imitator — classification, distribution, maximum length and water range.
• ScotCat: Brachyrhamdia imitator — the False Cory name, mimicry ideas, aquarium size, tank mates, diet and water range.
• Welsfans catfish database: Brachyrhamdia imitator — total length, recommended tank length, temperature and wild stomach contents.
• Seriously Fish: Brachyrhamdia rambarrani (genus notes) — genus-level notes on Brachyrhamdia: how to tell them from Corydoras, diet, social needs and spawning.
• Seriously Fish: genus Brachyrhamdia — the Brachyrhamdia species covered by Seriously Fish and their care ratings.
• OATA: How to look after freshwater catfish — UK guidance on catfish water quality, spines, acclimatisation, feeding and weekly water changes.
• Tropical Fish Co delivery policy — current dispatch days and Live Arrival Guarantee terms.