Why Breed Corydoras?
Corydoras catfish (affectionately called cories) are among the most beloved community fish — peaceful, active, always scurrying along the substrate hunting food. Over 170 species are scientifically described, ranging from the common bronze cory to the prized panda cory to rare collected species that sell for $100+ per fish.
Breeding cories is achievable and rewarding. Unlike many egg layers that produce hundreds of tiny eggs, cories produce 20-50 larger eggs per spawn, and parents generally ignore the eggs rather than eating them. Fry raising is straightforward. And the unique spawning behavior — the T-position — is one of the most distinctive in freshwater fish.
Species Selection for Breeders
Easy-to-breed species: bronze cory (Corydoras aeneus, also albino bronze), peppered cory (Corydoras paleatus), sterbai cory (Corydoras sterbai). These breed in standard community tanks with minimal intervention.
Intermediate species: panda cory (Corydoras panda), Julii cory (often Corydoras trilineatus sold as Julii), bandit cory (Corydoras metae). Require cooler water triggers and more attentive parameter management.
Advanced species: pygmy corydoras (Corydoras pygmaeus, habrosus, hastatus), adolfoi, imitator, and rare collected specimens. These need soft acidic water, specific conditioning, and experienced handling.
Start with bronze or peppered cories. Once you have their spawning pattern mastered, the skills transfer to more challenging species.
Tank Setup for Corydoras Spawning
Breeding tank: 10-20 gallons, sand or very fine smooth gravel substrate, dense plantings (java moss, amazon sword, vallisneria), sponge filter (fry safe), heater, and flat surfaces for egg deposition (glass walls, broad plant leaves, slate).
Social structure: cory breeding works best with multiple females and 1-2 males. A 2:1 or 3:1 female:male ratio is ideal. Single pairs often fail to spawn; larger groups induce competition and excitement that triggers breeding.
Water parameters for breeding: soft acidic water is preferred by most species. pH 6.4-7.0, GH 2-6, and tannin-stained from driftwood or Indian almond leaves. The trigger is often a significant drop in temperature and pH combined with a major water change — mimicking rainy season conditions.
Conditioning: feed heavily for 2 weeks before breeding attempts. Varied diet: frozen bloodworms, live blackworms, tubifex, sinking catfish pellets, and brine shrimp. Well-fed females develop visibly rounded bellies.
The T-Position — Cory Spawning in Action
Cory spawning is triggered by a cool water change — 30-50% water change with water 3-5°F cooler than the tank. This mimics the monsoon rains of South America that flood their native streams.
Within hours of the water change, breeders show active behavior: rapid swimming, males chasing females, all cories clustered together. The actual spawning involves the famous T-position: the male positions his body perpendicular to the female, forming a T-shape. His vent lines up with her barbels. The female receives sperm in her mouth and uses it to fertilize eggs she then deposits on a surface.
This spawning method is unique to corydoras and a few related genera. Why it evolved is debated — the sperm travels through the females digestive tract to fertilize eggs — but it is 100% reliable when it happens.
Females lay eggs in clusters of 2-6 on vertical surfaces: glass walls, broad leaves, filter tubes, tank decor. Total spawning session produces 20-80 eggs. Parents do not guard eggs but generally do not eat them either.
- ✦Cool water change (3-5°F drop) is the main spawning trigger
- ✦T-position: male perpendicular to female, sperm transferred via female mouth
- ✦Eggs deposited in clusters on vertical surfaces
- ✦Multiple females dramatically increase spawn success rates
Egg Collection and Hatching
Eggs can be left in the parent tank (cories rarely eat eggs) or transferred to a separate hatching container for better survival. The transfer method: carefully roll eggs off the surface with your finger (cory eggs are very sticky and tough) and move to a small tank or breeder container.
Hatching container: 1-2 gallon setup with strong air stone for water movement, dechlorinated water matching parent tank parameters, and a drop of methylene blue to prevent fungal infection. No filter needed for the first few days.
Incubation: 3-5 days depending on temperature (warmer = faster hatching, but 76-80°F is safe). Eggs darken as embryos develop, and tiny fry are visible through the translucent shell near hatching time. Remove any white (fungused) eggs immediately — they infect neighboring eggs rapidly.
First food: hatched fry have a yolk sac for the first 2-3 days, then need first food. Offer microworms, baby brine shrimp (BBS), or crushed fry powder. BBS after 5 days are ideal. Daily water changes (20%) are mandatory in the small rearing container.
Raising Cory Fry
Cory fry grow slowly compared to livebearers but steadily. Week 1: tiny, hugging surfaces, eating microorganisms. Week 2-3: actively swimming, eating BBS. Week 4-6: coloring up, eating crushed flake and sinking pellets. Month 2-3: 0.5-0.75 inch, ready to move to grow-out tank. Month 4-6: sellable adult size.
Grow-out tank: 10-20 gallons, same parameters as parent tank, sponge filter, sand substrate. Feed 3-4 times daily with varied diet. Do weekly 25% water changes.
Selling: cory fry command good prices from local aquarium clubs, fish stores, and online sales. Rare species (sterbai, panda, adolfoi) fetch $8-20 per fish. Common species (bronze, peppered, albino) $3-6 each. A single successful breeding produces 30-80 sellable fry.