Quick Facts
- Common Names: Cory Catfish, Cory Cats, Corydoras, Armored Catfish
- Scientific Name: Corydoras spp. (170+ recognized species)
- Adult Size: 1-3 inches (2.5-7.5 cm), depending on species
- Lifespan: 5-10 years; up to 20+ years with exceptional care
- Care Level: Beginner
- Temperament: Peaceful
- Diet: Omnivore
- Minimum Tank Size: 20 gallons (10 gallons for dwarf species)
- Temperature Range: 72-78°F (22-26°C)
- pH Range: 6.5-7.8
- Water Hardness: 2-12 dGH (soft to moderately hard)
- Breeding Difficulty: Easy to Moderate
- Native Range: South America (Amazon Basin to Atlantic coast, Trinidad to Argentina)
Introduction
If you’re looking for a peaceful, entertaining bottom-dweller that brings personality to your aquarium, Corydoras catfish are hard to beat. These happy-go-lucky little fish scuttle around the tank like underwater puppies, constantly foraging and socializing with their tankmates. With over 170 recognized species (and hundreds more awaiting classification), there’s a Cory to fit every aquarium and experience level. This guide covers everything you need to know to keep these armored catfish healthy and thriving.
Video Overview
Appearance
Corydoras catfish have a distinctive stocky body covered in two rows of overlapping bony plates called scutes, which give them their “armored catfish” nickname. These armor plates protect them from predators while remaining flexible enough for easy swimming. Most species are 1-3 inches long with a slightly arched back and a flattened belly perfectly adapted for bottom dwelling.
Their most charming feature is their whisker-like barbels—three pairs of sensitive feelers around their mouth that they use to probe substrate for food. Think of these barbels as their fingers, constantly feeling and searching for tasty morsels buried in the sand.
Colors and patterns vary dramatically between species. Bronze and albino Corys (Corydoras aeneus) are the most common, with metallic bronze bodies or creamy white coloring. Panda Corys sport bold black patches around their eyes. Emerald Corys shimmer with iridescent green. Peppered Corys display salt-and-pepper speckling.
All Corydoras have sharp, slightly venomous spines on their dorsal and pectoral fins for protection—handle with care and never try to catch them with bare hands!
Gallery
Creating the Right Environment
Corydoras do best when their tank mimics their natural South American streams—soft substrate, plenty of hiding spots, and gentle water flow.
Substrate is critical. Soft sand or smooth, rounded gravel protects their sensitive barbels from damage. Sharp-edged gravel creates microscopic wounds that can lead to barbel infections and starvation. Pool filter sand is ideal and affordable. A dark substrate also helps these fish feel secure since they’re prey species in the wild.
Plants and hiding spots reduce stress. Dense vegetation makes Corys feel safe. Java fern, Amazon swords, crypts, and dwarf hairgrass work beautifully. Add caves, driftwood, and low-lying plants like Java moss where they can rest during the day. They’re most active at dawn and dusk but will be out and about all day in a well-planted tank.
Gentle filtration matters. These fish come from slow-moving streams, so strong currents stress them out. Use a sponge filter or adjust your filter output to create gentle flow. Good water circulation is important, but they shouldn’t be fighting the current.
Care Basics
Water: Keep temperature at 72-78°F, pH between 6.5-7.8, and hardness at 2-12 dGH. Commercially bred Corys tolerate a wider range than wild-caught fish, but stability is more important than hitting exact numbers. They’re adaptable but hate sudden changes.
Tank Size: Dwarf species (Pygmy, Habrosus) can live in 10 gallons, but most Corydoras need 20 gallons minimum. A 30-gallon tank is ideal for keeping proper groups and providing adequate swimming space along the bottom.
Food: Corydoras are NOT algae eaters and must be specifically fed. They need sinking foods that reach the bottom before other fish devour everything. Feed high-quality sinking pellets, bottom-feeder wafers, and shrimp pellets daily. Supplement twice weekly with frozen or live foods like bloodworms, blackworms, brine shrimp, and daphnia. They’re enthusiastic eaters but can be outcompeted in community tanks—watch to make sure they’re getting enough food.
Equipment: Use a gentle sponge filter or adjust your filter output to reduce flow. Include a heater to maintain stable temperature. Always cover the tank with a tight-fitting lid—Corys dart to the surface regularly to gulp air and can jump out during their enthusiastic surface trips.
Maintenance: Change 10-25% of water weekly to prevent nitrate buildup. Corydoras are highly sensitive to nitrates, which cause barbel infections and stress. Test water regularly and keep ammonia and nitrite at 0 ppm. When cleaning, disturb the substrate minimally to avoid releasing bacteria into the water column.
Behavior
Corydoras are active, social fish that bring constant entertainment to any tank. They spend most of their time scooting along the bottom, using their barbels to probe sand and gravel for food particles. Watching them work is like seeing tiny vacuum cleaners in action.
They’re natural shoaling fish that crave company. In groups of six or more, they gain confidence and display fascinating social behaviors—following each other around, resting together in plant shade, and occasionally performing synchronized surface breathing dashes. Lone Corys often hide and become stressed.
One quirky behavior surprises new owners: Corydoras regularly dart from the bottom to the surface, gulp air, and zoom back down. This is completely normal. They can breathe air through their intestines, which helps them survive in low-oxygen environments. If they do this excessively, however, check your water quality—it may signal oxygen depletion.
They’re peaceful to a fault and won’t bother anyone. They ignore other fish, won’t nip fins, and even leave newborn shrimp alone (though they might accidentally eat shrimp fry if they stumble upon them).
Tank Mates
Good choices: Corydoras are perfect community fish that get along with almost any peaceful species. Tetras (Neon, Cardinal, Ember), Rasboras, small Danios, Guppies, Mollies, Platies, Dwarf Gouramis, Honey Gouramis, Kuhli Loaches, Otocinclus, Bristlenose Plecos, and peaceful Rams all make excellent companions. They can even be kept with Angelfish and Discus in larger tanks. Snails (Mystery, Nerite, Ramshorn) and shrimp (Cherry, Amano, Ghost) are also safe tankmates.
Be careful with: Goldfish get too large and will try to eat Corydoras. African cichlids require hard water that doesn’t suit Corys. Very fast, aggressive eaters like some barbs may outcompete Corys for food.
Avoid: Aggressive or territorial cichlids (Oscars, Jack Dempseys, Texas Cichlids), Pufferfish, Crayfish, and large predatory fish that might eat or injure these gentle bottom-dwellers.
Group size: Keep at least 6 Corydoras of the same species together. They can mix species and will often shoal together, but same-species groups display more natural behavior. Larger groups of 10-15 are even better.
Common Health Issues
Ich (White Spot Disease): Small white spots appear on skin, fins, and gills. Caused by parasites, often triggered by stress or temperature fluctuations. Treat by raising temperature to 82°F gradually, increasing aeration, and using ich medication. Quarantine new fish for 2-3 weeks to prevent introduction.
Barbel Damage and Infections: Damaged or shortened barbels result from sharp substrate, high nitrate levels, or poor water quality. Barbels may become red, infected, or completely worn away. Prevent by using soft sand substrate, keeping nitrates below 20 ppm through regular water changes, and maintaining pristine water quality. Barbels can regrow in 4-8 weeks if conditions improve.
Red Blotch Disease: Red or pinkish sores appear on the belly and flanks, often after shipping stress or environmental stress. Caused by bacterial infection triggered by poor water conditions, sudden pH changes, or exposure to pure oxygen during transport. Treat with broad-spectrum antibiotics (tetracycline) and maintain stable water parameters. Adding 1-2 teaspoons of aquarium salt per gallon can help during treatment.
New fish: Always quarantine new Corydoras for 2-3 weeks before adding to your main tank. This prevents disease introduction and gives them time to recover from shipping stress.
Lighting & Appearance
Corydoras prefer moderate to subdued lighting that mimics their naturally shaded stream habitats. Bright lighting can stress them and make them hide more. They look best under standard community tank lighting with plenty of shaded areas provided by floating plants or dense vegetation.
A dark substrate really makes their colors pop. Bronze Corys develop richer metallic sheens against dark sand. Panda Corys’ black patches stand out more dramatically. Emerald Corys’ iridescent greens become more vibrant.
Tannin-stained water from driftwood or Indian almond leaves creates a natural biotope look and provides beneficial properties, though it’s not required. The brown tint can actually enhance the viewing experience and reduce stress.
Standard photoperiod of 8-10 hours works well. Corys don’t have strong lighting preferences but appreciate consistent day/night cycles.
Breeding
Corydoras are surprisingly easy to breed in home aquariums, and many aquarists report unexpected spawning without special effort. Most species follow similar breeding patterns.
Breeding Setup: While Corys may spawn in community tanks, a dedicated breeding tank increases fry survival. Use a bare-bottom or sandy 20-gallon tank with large rocks and broad-leafed plants (Java fern, Anubias) for egg-laying sites. Include a sponge filter for gentle circulation.
Sexing: Females are noticeably larger, rounder, and thicker-bodied when viewed from above. Males are slimmer and smaller. Wait until fish are 6-12 months old for accurate sexing.
Conditioning: Feed high-quality protein-rich foods (live blackworms, frozen bloodworms, brine shrimp) for 2 weeks before breeding. Keep the group well-fed and healthy.
Triggering Spawning: Perform a 50% water change with water 2-4°F cooler than tank temperature to simulate rainy season. This often triggers spawning within 24-48 hours. Males will chase gravid females, eventually forming the “T-position” where they embrace to transfer sperm.
Egg Laying: Females lay 10-50 sticky eggs on plants, glass, rocks, and decorations. They’ll often clean sites with their mouths before depositing eggs. The entire process takes 3-6 hours.
Raising Fry: Remove adults immediately after spawning—they’ll eat the eggs. Eggs hatch in 3-7 days depending on temperature. Fry have yolk sacs for the first few days, then need newly hatched brine shrimp, vinegar eels, or powdered fry food. Maintain pristine water quality with small daily water changes. Fry grow slowly but reach juvenile size in 6-8 weeks.
Corydoras breeding is commonly done in home aquariums, making them perfect for beginners wanting to try breeding projects.
FAQ
Q: How many Corydoras catfish should I keep together?
A: Keep at least 6 of the same species. They’re social schooling fish that feel most secure and display natural behaviors in groups. Larger groups of 10-15 are even better.
Q: What size tank do Corydoras need?
A: Dwarf species can live in 10 gallons, but most standard Corydoras need at least 20 gallons. A 30-gallon tank is ideal for maintaining proper groups.
Q: What substrate is best for Corydoras catfish?
A: Soft sand or smooth, rounded gravel. Sharp-edged gravel damages their sensitive barbels. Pool filter sand works perfectly.
Q: Are Corydoras catfish good for beginners?
A: Yes! They’re hardy, peaceful, adaptable, and easy to care for. They help keep tanks clean and are compatible with most community fish.
Q: Do Corydoras eat algae?
A: No, Corydoras are not algae eaters. They need sinking pellets, wafers, and frozen/live foods. They must be specifically fed to ensure adequate nutrition.
Q: Why do Corydoras swim to the surface?
A: They can breathe air and naturally gulp oxygen from the surface. This is normal behavior. Excessive surface gasping may indicate low oxygen or poor water quality.
Conclusion
Corydoras catfish are the perfect community fish—peaceful, entertaining, beginner-friendly, and endlessly charming. Their active personalities and social behaviors make them fascinating to watch, while their hardiness makes them forgiving of minor mistakes. Keep them in groups on soft substrate, feed them well, and maintain clean water, and you’ll have happy Corys thriving for years. Ready to add these delightful bottom-dwellers to your tank? You won’t regret it.
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Related Guides
- Neon Tetra Care Guide: Perfect mid-level tankmate for Corydoras in planted community tanks
- Cardinal Tetra Care Guide: Another peaceful schooling fish that thrives in similar water conditions
- Guppy Care Guide: Colorful top-dwellers that complete the community tank with Corys on the bottom