Freshwater Fish · Catfish
Sterba's Corydoras
Corydoras sterbai
The polka-dot cory that likes it warmBeginner
- Lifespan
- 5-10 years (sometimes longer)
- Size
- 6-7 cm (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 does well at ordinary corydoras temperatures but also stays comfortable up at the 28-30C (82-86F) that discus keepers run, which makes it the standard cory for warm-water tanks where the Bronze Corydoras would struggle.
- 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 Corydoras haraldschultzi, which reverses the pattern with dark spots on a pale ground; on sterbai the head is dark and the spots are pale.
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.
- 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 75 litres (20 US 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 75-litre 20-gallon long, 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 24-28C (75-82F) with tolerance to 30C (86F), pH 6.0-7.6, soft to moderately hard (roughly 2-15 dGH), and low nitrate in a fully cycled tank.
- 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.
Supplies
Setup
- Tank and stand
- Filter
- Heater and thermometer
- Substrate, plants and decor
- Liquid test kit
- Dechlorinator and starter supplies
Ongoing
- Sinking wafers or tablets for bottom-feeders
- Algae or spirulina wafers
- Frozen bloodworm, daphnia and brine shrimp
- Untreated aquarium driftwood (essential for clown plecos)
- Courgette, cucumber and spinach for blanching
- Veg clip or a stainless veg skewer
- Feeding tongs or a pipette for target-feeding
- Fine sand substrate for corydoras foraging
Safe substrate: Inert aquarium gravel · Fine, smooth sand · Aquasoil for planted tanks
Care routine
Daily
- Check temperature and equipment
- Head-count and look everyone over
- Sinking food at lights-out
Weekly
- Top up evaporationevery 3 days
- Check belly profiles
- Clean glass and clear algae
- Test the water
- Water change and gravel vacuum
Monthly
- Trim and thin the plantsevery 2 weeks
- Check supplies and reagent dates
- Check the driftwood
- Rinse the filter media
Less often
- Replace chemical filter media (Carbon/Purigen)every 2 months
Vet: Quarterly bottom-dweller review — every 3 months
Top resources for more info
Independent creators and organisations we would send a friend to. We have no affiliation with any of them, and nothing here is sponsored. Links checked 2026-09-19.
YouTubers
Girl Talks FishCare how-tos by fish type, tank setup and beginner mistakesAquarium Co-OpSpecies care guides, filtration and fish health (run by a retailer)Prime Time AquaticsSpecies profiles, stocking and water chemistry explained plainly
Sites
Go deeper
Diet
- 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
- 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 your enclosure big enough?
Minimum volume75 litres (20 US gallons)
CompanyCannot be kept alone. The minimum is 6, and the space above is for that group.
Is this urgent?
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.
NowFish gasping at the surface, or crowding the filter outflowIncrease surface agitation immediately, then test the water. Either the oxygen has crashed or the gills are being chemically burned. Both are hours-scale problems.
NowSudden 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 point at the water or the equipment, not at a pathogen.
NowToday
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.
TodayWhite 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.
TodaySoon
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 daysNever 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.
What it really costs
Setup, monthly, first year and across a whole life, itemised and with the electricity worked out from the actual wattage. Published figures for the same animal disagree by a factor of four, so the calculator shows ranges rather than picking one.
Bedding and substrate
Substrate in an aquarium is a filter as much as a floor. Most of the biology lives in and on it.
Safe
Inert aquarium gravelRinse thoroughly before use. Grain size should be too large to swallow and too small to trap food.
safeFine, smooth sandCorrect for corydoras, kuhli loaches and anything that sifts. Their barbels wear away on sharp gravel.
safeAquasoil for planted tanksExcellent for plants, but it leaches ammonia for the first weeks. Cycle around it; do not stock into it.
safeBare bottomLegitimate for quarantine and grow-out tanks. Easy to clean, but it holds far less biological filtration.
safeWith a caveat
Crushed coral or aragoniteDeliberately raises hardness and pH. Correct for rift-lake cichlids, wrong for soft-water species.
with a caveatVery deep sand bedsAnaerobic pockets form below about 5 cm in still sand. Either keep it shallow or keep it stirred.
with a caveatPainted or coated gravelUsually fine, but coatings chip. Test a handful in a jar for a week first.
with a caveatNever
Sharp or angular gravel with bottom-dwellersWears down barbels and leads to infection in corydoras and loaches.
neverAnything containing metal, limestone of unknown origin, or shells in a soft-water tankSlowly alters chemistry in ways that are hard to diagnose later.
neverThis is our general list for freshwater fish. We have not built one specific to Catfish yet.
My kit says 0.25 ppm. Is that dangerous?
A liquid kit measures total ammonia, but only the un-ionised fraction is really toxic, and that fraction is governed by pH and temperature — each whole pH unit multiplies it roughly tenfold. So the same reading can be nearly harmless in one tank and lethal in another; this works out which one you are in.
Compare with other animals
The same axes for every animal, side by side — the way the guides are written makes that a fair comparison rather than two articles.
Keep going
Catfish, side by side
Same axes, same care guides — the honest way to choose between types.
See all Catfish side by side →
