Freshwater Fish · Catfish

Sterba's Corydoras

Hoplisoma sterbai

The polka-dot cory that likes it warmBeginner

Lifespan: 5-10 years (sometimes longer)
Size: 2.4-2.7 in; females larger
Social needs: Shoaling - keep 6+ together, more is better
Time: Low-moderate (daily feed, weekly water changes)
Cost: Low-Medium
Diet: Omnivore (bottom-feeder)

Overview

What is this animal?

Sterba's Corydoras is a small armoured catfish from the upper Rio Guapore basin on the Brazil-Bolivia border, patterned with rows of fine white-to-cream spots over a dark head and body and set off by warm orange pectoral fins.
Its defining practical trait is heat tolerance: it is at home at 75-82°F and copes with the warm end better than most cories, which is why it is the usual cory for discus tanks where the Bronze Corydoras would struggle.
Run such a tank at the cooler end of discus temperatures, about 82°F; treat 86°F as a tolerance rather than a home, and add extra aeration.

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Virtually all fish sold today are tank-bred, hardy, and genuinely beginner-friendly, provided the basics are met: a shoal of six or more, soft sand, and food that actually reaches the bottom.
It is often confused with Brochis haraldschultzi, which reverses the pattern with dark spots on a pale ground; on sterbai the head is dark and the spots are pale.
A 2024 revision of the corydoras group moved that look-alike from Corydoras to Brochis and sterbai itself to Hoplisoma, so it is now Hoplisoma sterbai, though shops still sell it as Corydoras sterbai.

Temperament

This is a peaceful, day-active shoaling catfish that must be kept in a group of six or more of its own species.
In proper numbers they forage in a loose pack, rest in piles, and show the characteristic corydoras eye-wink; kept alone or in pairs they hide and waste away.

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They are the classic bottom-dwellers for discus, cardinal tetras, rummy-nose tetras, and other warm-water community fish.
Avoid large cichlids or anything big enough to try swallowing them, because the locking spines can lodge in a predator's throat and kill both fish.
They bother no tankmate and are among the more willing corydoras to spawn in home aquaria, laying adhesive eggs on the glass after cool-water changes.

A good fit for

Discus and other warm-water community tanks
Beginners wanting a hardy, long-lived cory
Tanks with soft sand substrate
Keepers who enjoy daytime bottom activity
A first try at breeding egg-laying catfish

Common mistakes to avoid

Keeping fewer than 6 - they need a shoal
Sharp gravel shredding their barbels
Low oxygen at discus-tank temperatures
Nets - their locking spines tangle and prick
Salt and copper medications they tolerate poorly
Treating them as clean-up crew, not feeding them

Enclosure

Minimum 20 gallons, for a group of 6

Cannot be kept alone. The minimum is 6, and the space above is for that group.

House a group of six in at least a 20-gallon long tank, and give more floor space for larger groups, prioritising footprint over height because these fish live on the bottom.
A soft sand substrate is non-negotiable, since sharp or coarse gravel erodes the sensory barbels they feed with.
Keep the water at 75-82°F with tolerance to 86°F, pH 6.0-7.6, soft to moderately hard (roughly 2-15 dGH), and low nitrate in a fully cycled tank.

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Furnish with driftwood, plants, leaf litter, and shaded resting spots, and leave open sand for foraging.
They dash to the surface to gulp air, so keep an air gap beneath a tight-fitting lid.
Warm water holds less oxygen, so at discus temperatures add extra surface agitation or an air stone.

Check your enclosure

Supplies

Setup

Tank and stand
Filter
Heater and thermometer
Substrate, plants and decor
Liquid test kit
Dechlorinator and starter supplies

Ongoing

Sinking pellets, wafers or tablets (corydoras)
Algae or spirulina wafers (bristlenose and otocinclus)
Frozen bloodworm, daphnia and brine shrimp (corydoras)
Untreated aquarium driftwood (for bristlenose plecos to rasp)
Courgette, cucumber and spinach for blanching (bristlenose and otocinclus)

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Veg clip or a stainless veg skewer (bristlenose and otocinclus)
Feeding tongs or a pipette for target-feeding
Fine sand substrate for corydoras foraging

Safe substrate: Fine, smooth sand · Smooth, rounded fine gravel (not for loaches or sand-sifting cichlids; sand is better for corydoras) · Bare bottom (quarantine and grow-out only)

Work out the cost

Care routine

Daily

Check temperature and equipment
Head-count and look everyone over
Sinking food at lights-out

Every few days

Top up evaporationevery 3 days

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Weekly

Check belly profiles
Test the water
Water change and gravel vacuum
Wipe the front glass only

Every few weeks

Trim and thin the plantsevery 2 weeks

Monthly

Check supplies and reagent dates
Check the driftwood
Replace or recharge chemical media, if you use any (skip it in a blackwater tank)
Rinse the filter media

Health review: Quarterly bottom-dweller review, every 3 months

Tools

Is your enclosure big enough?Check your measurements against the recommended size What will it cost?Setup, monthly and over its whole life, itemised Is this ammonia reading dangerous?Works out the toxic part from your pH and temperature

Care in depth

Diet

Omnivore (bottom-feeder)

Sterba's Corydoras is an omnivore that must be fed deliberately, never left to survive on leftovers.
Offer sinking wafers, pellets, and tablets, supplemented several times a week with frozen or live bloodworm, daphnia, and brine shrimp.

Make sure food gets past faster mid-water fish; feeding after lights-out or dropping food at several spots helps the cories get their share.
Quiet, slow starvation in busy community tanks is the most common way this species fails.
Vacuum the sand regularly, because food rotting in the substrate drives the barbel infections that cost them the ability to find food.

Health

Signs of good health, and the common problems

The main preventable problems are barbel erosion and red blotch disease, both driven by sharp or dirty substrate and poor water quality.
They are sensitive to salt and copper-based medications, so treat at reduced doses or choose catfish-safe alternatives.
Watch barbel length, breathing rate, and skin condition, and quarantine all new arrivals.

The orange pectoral spines lock outward under stress; they tangle hopelessly in fine nets and can give a mildly venomous prick, so move these fish with a rigid container or a bag rather than a net.
Corydoras can also release a stress toxin in cramped transport bags, so bag them in generous water, a few fish per bag, for short journeys only.
A well-kept sterbai commonly lives 5-10 years and can pass a decade with excellent care, so plan for a long-term resident.

Is this urgent?

6 warning signs and how fast to act, 3 of them right away

In a fish tank the patient is usually the water. Test before you treat: dosing a healthy tank for a disease it does not have makes things worse.

Go now

Any detectable ammonia or nitrite in a stocked tankLarge water change now with dechlorinated, temperature-matched water. Stop feeding. Test again in 12 hours. Both are directly toxic. How toxic the ammonia reading is depends on pH and temperature, so the same number can be harmless or lethal.

Now

Fish gasping at the surface with fast gill movement, or crowding the filter outflowIncrease surface movement now (gently in a betta or gourami tank, without creating a strong current), then test the water. Either the oxygen has crashed or the gills are being chemically burned. Both are hours-scale problems. Bettas, gouramis and corydoras rise to gulp air as part of normal breathing; the warning is constant gulping, fast gill movement, or the whole group hanging at the top.

Now

Sudden deaths, more than one fish in a dayTest ammonia, nitrite, nitrate and temperature before doing anything else. Do not add medication yet. Multiple simultaneous deaths usually point at the water or the equipment rather than a pathogen, so rule those out first.

Now

Today

Flashing: repeatedly scraping against decor or substrateTest the water, then look closely for parasites. Irritation is either chemical or parasitic; the test tells you which before you medicate.

Today

White salt-grain spots over the body and finsBegin the appropriate treatment today and check the temperature. The parasite's life cycle is temperature-driven, and it multiplies with every cycle you wait.

Today

Soon

Clamped fins, hiding, or refusing food for more than two daysTest the water and review recent changes. Usually the earliest visible sign of a parameter drifting.

A few days

Never add a new fish to a tank that is not fully cycled, and never treat blind. A test kit is cheaper than the fish.

This is general guidance for a healthy adult, not a diagnosis. An exotics vet who knows your animal always overrides it, and the time to find one is before you need one.

Bedding and substrate

3 safe, 4 with a caveat, 2 to avoid

Substrate in an aquarium is a filter as much as a floor. Most of the biology lives in and on it.

Safe

Fine, smooth sandCorrect for corydoras, kuhli loaches, eartheaters such as rams and acaras, and anything else that sifts or burrows. Barbels wear away on sharp gravel.

safe

Smooth, rounded fine gravel (not for loaches or sand-sifting cichlids; sand is better for corydoras)Rinse thoroughly before use. Grain size should be too large to swallow and too small to trap food. Kuhli loaches need sand to burrow into and rams and acaras sift mouthfuls of it; bronze and panda corydoras manage on smooth fine gravel, but sterbai corydoras need sand.

safe

Bare bottom (quarantine and grow-out only)Legitimate for quarantine and grow-out tanks. Easy to clean, but it holds far less biological filtration, and it is no long-term home for burrowing loaches or sand-sifters.

safe

With a caveat

Crushed coral or aragoniteDeliberately raises hardness and pH. Correct for rift-lake cichlids, wrong for soft-water species.

with a caveat

Aquasoil for planted tanksExcellent for plants, but most active soils soften the water and pull pH and KH down for months, and many leach ammonia for the first weeks. Right for soft-water species; wrong for hard-water animals (livebearers, rainbowfish, goldfish, and snails, whose shells erode in soft, acidic water) unless you test GH and KH and remineralise. Cycle around it; do not stock into it.

with a caveat

Very deep sand bedsAnaerobic pockets form below about 2 inches in still sand. Either keep it shallow or keep it stirred.

with a caveat

Painted or coated gravelUsually fine, but coatings chip. Test a handful in a jar for a week first.

with a caveat

Never

Sharp or angular gravel with bottom-dwellersWears down barbels and leads to infection in corydoras and loaches.

never

Anything containing metal, limestone of unknown origin, or shells in a soft-water tankSlowly alters chemistry in ways that are hard to diagnose later.

never

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