Sterbai Cory (Corydoras sterbai)

Origin & Etymology

The species name *sterbai* honours Günther Sterba (1922–2020), a German ichthyologist, aquarist, and author who dedicated much of his career to freshwater fish of the Amazon basin. Sterba is best remembered for his encyclopaedic work *Freshwater Fishes of the World*, first published in 1959, which became the standard reference for aquarium fish for decades and was translated into numerous languages. The Sterbai cory was formally described by Knaack in 1962, who named it in recognition of Sterba’s contributions to the understanding and popularisation of South American catfishes.

The genus *Corydoras* is one of the most species-rich genera of freshwater fish, with over 170 described species and many more awaiting formal description. The name *Corydoras* derives from the Greek *kory* (helmet) and *doras* (skin), referring to the distinctive double row of bony scutes — called plates or scutes — that form the armoured flanks of all callichthyid catfishes. These plates are not mere decoration; they are the fish’s principal defence against predation, making corydoras effectively rigid-bodied and difficult for most predators to swallow.

The Sterbai cory was collected from the upper Guaporé River, which forms part of the border between Brazil and Bolivia. The Guaporé is a clear, warm, slow-moving river with sandy and rocky substrates, dense aquatic vegetation in the margins, and water chemistry that can vary from moderately soft and slightly acidic to near neutral — which explains the Sterbai cory’s tolerance for a fairly broad pH and hardness range.

Aquarium Setup Guide

The substrate is the single most important element of a Sterbai cory tank. In nature, these fish forage constantly through sand and fine sediment, pushing their barbels through the substrate to detect buried food. Coarse gravel or sharp-edged substrate will wear down and eventually erode the barbels — the sensory whiskers around the mouth — causing chronic bacterial infections that are difficult to treat. Use fine-grain sand (0.1–0.5 mm particle size) or smooth, rounded substrate specifically sold for corydoras. Dark sand shows off the white spotting to best effect.

A 60-litre tank is the minimum for a school of six — the recommended group size for this social species. A larger group of eight to twelve in a 90-litre tank produces much more natural behaviour, with the fish foraging, resting, and swimming in coordinated groups. Provide shelter in the form of driftwood, smooth-edged caves, and areas of dense planting, as corydoras appreciate retreat spots and will use them regularly between foraging bouts.

Sterbai corys are compatible with most live plants and will not disturb roots. Java fern, Anubias, and Vallisneria are all excellent choices. Avoid very delicate carpet plants on the substrate, as the corys’ constant foraging activity may uproot them. The fish are active and entertaining, but they are not jumpers — a lid is still recommended mainly to prevent overheating problems from open-top evaporation.

Nutrition & Diet

Corydoras sterbai are opportunistic omnivore bottom-feeders in the wild, consuming whatever edible matter sinks to the substrate — invertebrates, detritus, plant material, and organic debris. In the aquarium, they require sinking foods specifically, as they are physically incapable of competing with mid-level or surface feeders. Sinking pellets and wafers designed for bottom-dwellers should form the staple diet; look for formulas with high protein content and a range of ingredients, as corydoras do best on dietary variety.

Supplement two to three times per week with frozen bloodworm, frozen daphnia, or frozen tubifex — all eagerly consumed. Sterbai corys are enthusiastic feeders for a corydoras species and will emerge actively at feeding time rather than waiting for food to drift to them. Blanched vegetables (spinach, zucchini, cucumber) are accepted occasionally and provide beneficial fibre. Feed in the evening or shortly after lights-out, as corydoras are naturally more active in lower light and will compete more effectively against daytime feeders.

Community Compatibility

The Sterbai cory’s greatest community asset is its temperature tolerance. Most corydoras species cap out around 25–26 °C and become stressed in the warm conditions preferred by discus, altum angels, and similar fish. The Sterbai cory is the practical solution — a genuine bottom-dwelling companion that can thrive at 28 °C, clean up substrate waste, and add a completely different visual layer to a warm-water showcase tank. Their armoured bodies and mild venomous spines mean they have effective natural defences; they should not be housed with large predatory fish, but they are far more robust than their peaceful temperament might suggest. The one practical precaution worth knowing: when handling or netting Sterbai corys, be aware that the pectoral fin spine can lock in an extended position and tangle in fine mesh nets — wet your hands if handling them directly, and use a container rather than a net where possible.

Available Colour Grades

In the trade, the wild-type Sterbai cory dominates and is the form most aquarists seek — its dark body with white spotting and the burst of orange at the pectoral fins creates one of the most distinctive silhouettes of any small catfish. The albino form appears occasionally and attracts attention, but is generally considered less striking. Colour intensity in the wild type varies with light and mood: fish kept on dark sand under subdued lighting display richer, higher-contrast patterning than those on light gravel under bright lights. The orange pectoral fin colouration is consistent across specimens and does not vary significantly with diet, making it a useful identification marker when distinguishing Sterbai cory from similar species such as *Corydoras haraldschultzi*, which has a similar spot pattern but lacks the orange fin colouration.

Acclimation & First-Week Care

Proper acclimation prevents shock and greatly improves survival. Never rush this process.

Step-by-Step Acclimation

1. Float the sealed bag in your aquarium for 15–20 minutes to equalise temperature.
2. Open the bag and roll down the edges to create a floating collar.
3. Drip acclimation: Add approximately ¼ cup of tank water to the bag every 5 minutes for 30–40 minutes.
4. Net and release — gently net the fish/shrimp and place them into the aquarium. Discard the bag water; never pour it into your tank.

First-Week Checklist

• Keep lights dimmed for the first 24–48 hours to reduce stress.
• Feed sinking wafers or frozen bloodworms — Corydoras are bottom feeders and won’t compete at the surface.
• Add in a group of 4+ for social comfort.
• Monitor ammonia and nitrite daily — any spike above 0.25 ppm warrants an immediate 25% water change.
• Observe for signs of disease (white spots, clamped fins, lethargy) and quarantine if needed.

Sydney Keeper Tips

Keeping Sterbai Corydoras in Sydney comes with specific advantages and challenges. Here’s what local keepers should know.

Sydney Tap Water

Sterbai Corydoras are unusual among Corydoras — they prefer warmer water (24–28°C), making them one of the few Corydoras compatible with Discus tanks. Sydney tap water parameters suit them well.

Seasonal Considerations

Their warm-water preference means Sydney’s summer is their comfort zone. In winter, keep heaters set to at least 25°C. Sterbais are one of the few Corydoras that won’t suffer in a heated tropical community.

Local Tips

• Sterbai Cories are the go-to Corydoras for Discus tanks in Sydney — they share the same temperature requirements.
• Feed sinking wafers after lights-out — you’ll see them foraging actively in the dark.
• Sand substrate is non-negotiable for all Corydoras — their barbels are damaged by gravel.

Frequently Asked Questions

How to Sex This Species

Sexing Corydoras sterbai is best done by viewing the fish from above rather than from the side. A mature female will be clearly broader across the body — she has a wider, rounder silhouette compared to the streamlined male. This difference is especially pronounced when the female is carrying eggs, but it is visible even in non-breeding condition in adult fish. In young or juvenile fish, the sex difference is not reliably apparent and attempts to sex them are likely to be inaccurate.

Colour and fin shape provide no reliable sex cues in this species — both sexes are identically patterned and fin lengths are not sexually dimorphic in the way seen in some other fish families. For breeding purposes, buying a group of six or more juveniles and allowing them to reach maturity together is the most practical approach, as a mixed-sex group is virtually guaranteed.

Getting the Water Right

The Sterbai cory stands apart from most corydoras in its genuine preference for warm water. While many cory species do best between 22–26 °C, Sterbai cory are naturally adapted to the warm upper Guaporé, where water temperatures regularly reach 27–28 °C. This makes them uniquely suited to discus tanks, angelfish setups, and other high-temperature communities where most corydoras would be uncomfortable over the long term. Keeping them at 26 °C as a daily baseline and allowing temperatures to reach 28 °C during breeding conditioning causes them no stress whatsoever.

Water quality is critical. As bottom-dwellers, Sterbai corys are directly exposed to any debris or waste that settles on the substrate. High nitrate levels are a particular hazard — corydoras are more sensitive to nitrates than many fish, and chronic exposure above 20 ppm leads to barbel erosion and bacterial infections. Perform weekly 25–30% water changes and syphon the substrate regularly. Bare sand bottoms are easier to keep clean than gravel, which traps waste. Dissolved oxygen should be high — especially at warmer temperatures where gas solubility drops; ensure the filter creates good surface movement.

How to Breed

Week -1 to -2

Conditioning

Feed group live and frozen foods; raise temperature

Day 0

Courtship

Males pursue female; T-position mating begins

Day 0–1

Egg Deposition

Female deposits batches of 2–6 eggs on chosen surfaces

Day 1–3

Egg Incubation

Transfer eggs or parents; eggs develop over 3–5 days

Day 4–6

Hatching

Fry hatch and absorb yolk sac over 48 hours

Day 7+

Free Swimming

Fry begin feeding; offer microworm and baby brine shrimp

Conditioning

Feed the breeding group generously with live or frozen bloodworm and daphnia for one to two weeks. The females should visibly round out as eggs develop. Raise the temperature gradually to 27–28 °C. Some breeders trigger spawning by performing a large (30–50%) water change with slightly cooler water (22–24 °C), mimicking the seasonal rain event that triggers breeding in the wild.

Courtship

When ready to spawn, males pursue the female around the tank in short, energetic chases. Spawning occurs in the characteristic corydoras T-position: the female positions herself perpendicular to the male and takes his milt into her mouth. She holds it briefly while selecting a spawning site — a clean surface such as broad plant leaves, the aquarium glass, or smooth decor — before pressing her cupped pelvic fins (which hold the fertilised eggs) against the surface and depositing them.

Egg Deposition

The female deposits eggs in small batches of two to six, carefully pressing them onto plant leaves, glass panels, or flat decor surfaces. Each batch is secured by natural adhesion. The process repeats throughout the spawning session, with a total of 30–100+ eggs typical for a healthy female. The eggs are large relative to fish size, spherical, and initially pale cream to green in colour.

Egg Incubation

Corydoras show no parental care after spawning and will eat the eggs if left in the same tank. Either remove the adults and leave the eggs in place (add a small airstone nearby for gentle circulation), or carefully peel the adhesive eggs from surfaces with a finger and transfer them to a small hatching tank. Keep the hatching tank at 26–27 °C and add a small amount of antifungal treatment (methylene blue at low dose, or a clean tank with good flow) to prevent fungal losses.

Hatching

At 26 °C, eggs typically hatch within 3–5 days. Newly hatched fry are relatively large and robust compared to many egg-scattering species. They absorb the yolk sac over approximately 48 hours, during which they require no feeding and should not be disturbed. Keep the hatching vessel clean, as decomposing unfertilised eggs can quickly foul the water.

Free Swimming

Free-swimming fry immediately exhibit the corydoras bottom-foraging behaviour, searching the substrate for food. Offer microworms, baby brine shrimp nauplii, or commercially prepared liquid fry food from the start. Fry grow steadily on this diet and begin to show their characteristic spotted patterning within four to six weeks. Move juveniles to the main tank once they reach 1.5–2 cm and are large enough not to be accidentally startled by larger tankmates.