Breeding Corydoras: Step-by-Step Guide for Cory Catfish

Corydoras are also known as cory catfish. They are small, peaceful freshwater fish from South America and are popular in community aquariums because they are social, hardy, and easy to keep in groups of six or more of their own kind. They also swim peacefully alongside tetras and other similar-sized community fish.

To breed corydoras, keep a group with more males than females (about 2 males to 1 female), feed them live or frozen foods, and then trigger spawning with a large water change (50-70%) using slightly cooler water and extra aeration. Repeat it daily until the females lay sticky eggs on the glass, plants, or decor. The eggs hatch in about 3 to 5 days, and the fry need tiny foods like microworms or newly hatched baby brine shrimp once their yolk sacs are gone.

“Corydoras” is the scientific name for cory catfish. This guide uses both names, and the advice applies to most commonly kept species.

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Corydoras Quick Facts

What Else Should You Know About Corydoras?

1. Females are larger and rounder than males. Bronze corys reach roughly 3 inches.
2. Corydoras lay eggs. They do not give birth to live young.
3. They eat both plant and animal foods, but their food must sink to the bottom.
4. Corydoras can gulp air at the surface and absorb oxygen through the gut, so don’t be alarmed when you see them dash up for a breath.
5. Well over 160 species have been described, though the exact number depends on how the group is classified.
6. They like occasional blanched zucchini or squash.

Where Do Corydoras Come From?

Corydoras live in slow-moving streams, rivers, ponds, and marshes across South America, usually in shallow, often murky water over soft bottoms.

The peppered cory (Corydoras paleatus) was described scientifically from specimens Charles Darwin collected during the voyage of HMS Beagle (1831-1836), which makes it one of the earliest corydoras known to science.

Do Corydoras Keep the Tank Clean?

Not really. Corydoras are popular because they are calm and get along with other fish, and they will pick through the substrate for leftover food. But they are not a cleanup crew. They need their own sinking food, and a group of them still produces waste.

What they do is keep the surface of the substrate turned over as they forage. That is one reason a soft sand or fine, smooth gravel substrate is best, since it protects the sensitive barbels around their mouths. Compact sand can build up pockets of gas, so stir it lightly now and then if you notice it going stale.

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What Do You Need Before Breeding Corydoras?

Corydoras will often eat their own eggs, so plan to separate the adults and the eggs. Corydoras can spawn in the community tank, but the eggs are easier to protect in a dedicated tank.

Set up the breeding tank first and cycle it fully. A cycled tank matters because eggs and fry are sensitive to ammonia and nitrite. If you are short of time, use a water conditioner and bottled beneficial bacteria, or seed the tank with a used sponge filter from an established tank. A brand-new tank can take about a month or longer to cycle.

A breeding tank can be simple. Aim for 10 gallons or more, with:

• A sponge filter, which is gentle enough for fry and for eggs. Breeders often prefer sponge filters for corydoras fry.
• A reliable heater, because corydoras are sensitive to temperature swings.
• A bare bottom or a thin layer of fine sand, which makes it easy to see and siphon the eggs.
• A few hiding spots, such as a large plant or a cave. Broken coconut shells work well. Java moss, crypts, and similar plants give the fish a place to lay eggs.

Keep the tank in a quiet spot out of direct sunlight, so you can control light and temperature. Start with water at 75-78°F and a pH of 6.0-8.0.

How Old Do Corydoras Need to Be to Breed?

Wait until your corydoras are about a year old and close to adult size. Males may be able to breed earlier, but spawning is hard on young fish, and size is a better guide than age. Fish mature at different rates, so judge by size and body shape, not just months.
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How Can You Tell Male and Female Corydoras Apart?

You can’t tell the sexes apart reliably in young fish. Once they are mature, look at the fish from above. Females are noticeably rounder and broader-bodied, especially when full of eggs, and they grow a little larger. Males are slimmer.

Do Corydoras Change Sex?

No. A cory that starts out male stays male, and the same is true of females. Apparent changes are usually a mistake in identifying the fish when they were young.

How Do You Get Corydoras to Spawn?

Here is the usual method:

1. Start with healthy fish. If you recently medicated the fish, wait a few weeks before trying to breed them.
2. Use a group, with more males than females. Breeders commonly use two males for every female, for example 4 males and 2 females, or 6 males and 3 females. A single pair often won’t spawn.
3. Condition them with food. For a week or two, feed live or frozen foods such as blackworms, baby brine shrimp, or daphnia, along with a good sinking pellet. Females should look visibly plump with eggs.
4. Trigger spawning with a cool water change. Do a large water change of 50-70% with water a few degrees cooler than the tank, and increase aeration and flow. This imitates the start of the rainy season. Repeat daily until the fish spawn. This is the trigger, not a routine: once the eggs are laid, go back to normal, smaller water changes.
5. Watch for the “T-position.” The male and female take turns chasing each other. The female then holds her pelvic fins together and the male presses against her, forming a T. She collects the eggs in that pouch and carries them to a clean surface.

Always treat new water with a dechlorinator and match the water chemistry as closely as you can.

How often can you breed corydoras? Once the fish are healthy and in good condition, they can spawn repeatedly. Give them a few weeks of rest and good feeding between rounds.

You will need a larger tank ready for the fry. They need about 4 to 5 weeks before they can safely join the group, and you will need room for all of them.

What Tank Conditions Do Breeding Corydoras Need?

Adult corydoras do best in a tank of about 20 gallons for a group of bronze corys, with a base of about 32 inches by 12 inches. Smaller species like pygmy corys need less room. They are active and social, so the tank should be long, not tall.

If they are constantly darting about, hiding, or look startled, the tank is probably too crowded.

A group of 6 or more is the minimum, because corydoras are social fish that become shy and stressed in small groups.

Which Equipment Is Best for a Breeding Tank?

• Heater: A stable temperature protects eggs and fry. Keep it steady at 75-78°F.
• Filter: A sponge filter is best. Canisters work for adult tanks but can suck up fry unless you cover the intake.
• Lighting: Use LED lights if you add live plants. Good light also helps you spot eggs and fry.
• Substrate: Sand or very smooth fine gravel protects the barbels. Sharp gravel can damage them and lead to infection.
• Plants: Don’t overdo it. A few trimmed plants give the fry cover without making the tank hard to clean.

What Are the Most Common Breeding Mistakes?

• Using a single pair. Corydoras do better in a group with more males than females.
• Not conditioning the fish. Females that aren’t plump with eggs usually won’t spawn.
• Making water changes with water that is too different. Use a few degrees cooler water, not ice cold, and always dechlorinate.
• Leaving the eggs with the adults. They will eat them.
• Rough substrate. Sharp gravel damages barbels, which can then become infected.
• Feeding the fry too early or too coarsely. Wait until the yolk sac is gone and offer food small enough to swallow.

What Should You Do After Corydoras Lay Eggs?

Remove the adults as soon as spawning ends, or move the eggs. Either way works, but handling eggs is easier in a bare tank, so moving the adults out is simpler for beginners. If you do move the eggs, roll them gently off the glass with a wet finger or use a soft tool, since the eggs are fragile.

Corydoras eggs typically hatch in about 3 to 5 days, depending on species and temperature. Warmer water speeds up hatching. Unfertilized eggs turn white or fuzzy, so remove them with a pipette before fungus spreads to healthy ones.

Do Corydoras Eat Their Own Eggs?

Yes, they often do. Adults will eat eggs and sometimes fry, so you should separate them. Whether this serves any purpose in the wild is not known.

How Do You Care for Corydoras Fry?

The fry live off their yolk sacs for the first couple of days after hatching, so don’t feed them until they are free-swimming and the yolk is gone. After that, feed small amounts two or three times a day.

For the first foods, offer powdered fry food, microworms, or newly hatched baby brine shrimp. Baby brine shrimp are a favorite, and the fry’s bellies turn reddish when they have eaten. As they grow, add small frozen foods like daphnia and finely crushed sinking pellets.

Keep the water clean with small, frequent water changes, because fry are sensitive to poor water quality. Siphon uneaten food as you go.

Weak or deformed fry may appear. If you want healthy breeding stock for the future, separate the weaker ones and don’t breed from them.

When the fry are big enough to join the main group, make sure the tank can hold everyone. If you can’t house them all, find new homes for the extra fish.

Frequently Asked Questions

Is it easy to breed Corydoras?

Fairly easy for a fish. Common species like the bronze and peppered cory often spawn with little encouragement if you keep a group with more males than females, feed live or frozen foods, and use a cool water change as a trigger. The hard part is protecting the eggs and raising the fry.

How often do Corydoras lay eggs?

Healthy, well-fed fish can spawn repeatedly, but give them a few weeks of rest and good feeding between rounds. Each round usually follows a trigger such as a large cool water change.

Will Corydoras breed in a community tank?

They can, but few eggs survive. Corydoras often eat their own eggs and sometimes the fry, and community tank mates will eat them too. Move the adults out after spawning, or move the eggs to a separate container or a dedicated breeding tank.

What is the easiest corydora to breed?

The bronze cory and the peppered cory. Both are hardy community staples that breed readily and accept ordinary foods, which is why they are the usual first choice for beginners.

How to trigger Corydoras to breed?

Do a large water change (50-70%) with water a few degrees cooler than the tank, and increase aeration and flow. This imitates the start of the rainy season. Repeat daily until they spawn. Well-conditioned fish fed live or frozen foods respond best, and a lone pair often fails, so keep a group with about 2 males to each female.

How long do corydoras eggs take to hatch?

Most corydoras eggs hatch in 3 to 5 days. Temperature and species change the timing, and warmer water hatches the eggs a little faster.