Cory catfish (any catfish in the genus Corydoras) are some of the most popular catfish in the pet trade. Their calm disposition, relatively small size, and willingness to cohabit with other fish, make them ideal for soft-water community tanks.
Whether you’re a seasoned fishkeeper or an absolute beginner, at least one species of cory will make your day.
In this article, we’ll take a closer look at everything you need to know to keep these fish successfully, including:
- Where cory catfish come from
- Different species of Corydoras
- Tank sizes these fish need
- How and what to feed your cory
- Breeding cory catfish
- The appropriate water parameters
- Their temperament and appropriate tank mates
Let’s get into it.
Cory Catfish in a Nutshell
- Origin: South America, covering large parts of the Amazon River Basin and tributaries that run into it.
- Natural Habitat: Slow-moving (and sometimes faster) rivers, swamps, lakes, and other bodies of water with a soft, siftable substrate.
- Size: Between one and five inches
- Temperament: Calm, docile, semi-social
- Tank Size: 10-gallon aquariums for smaller species, 20-gallons or more for larger species
- Water Parameters: 72-78°F; soft (18-220 PPM), slightly acidic (7.0-8.0)
- Water Changes: 35% weekly
- Lifespan: 5 years or more, under ideal conditions.
Cory Catfish: Background and Origin
The genus Corydoras was officially described in 1803 and has quickly expanded over the years. Scientists have described more than 160 species, making it one of the largest (if not the largest) genera of Neotropical fish. They belong to the family Callichthyidae, which includes all the armored catfish.
Sometimes, people to understand the various names of these catfish. Corydoras is the Latin name of the genus that all cory catfish belong to. Cory, cory cat, and other similar terms, are simply the hobbyist’s way of making them easier to reference. These terms aren’t mutually exclusive to any one species, but refer to all species in this group.
These fish have a distribution that covers a large swathe of South America, starting just east of the Andes mountain range, and extending to the Atlantic coast.
One of the reasons for the impressive number of species in this genus includes the distribution range for each species. Individual species tend to have tiny distribution ranges.
For instance, the Sterbai Cory, Corydoras sterbai only occurs in small parts of the Guapore River. The Panda Cory, Corydoras panda only occurs in a few areas of the Upper Amazon.
The Peppered Cory, Corydoras paleatus, and Bronze Cory, Corydoras aeneus, have some of the broadest distributions. They occur through large parts of the Amazon Basin.
Some believe it’s likely that groups of fish have become separated over the years. As smaller groups of these animals were left to their own devices, they adapted to take advantage of minor differences in their region.
After a while, they adapted significantly enough to become species in their own right. This phenomenon has been well-documented among riverine Cichlids.
Most Popular and Hardiest Cory Cats
Most Corydoras catfish are easy to care for. They’re not messy, they help keep the tank clean, and they’re easy to keep alive. Their only real requirement is soft water with plenty of oxygen.
Because they’re so adaptable, they’re incredibly popular. Some species are more popular than others, though. Some of the most popular cory cats (and the easiest to keep alive) include:
- Sterbai Cory – Incredibly popular due to its medium size and polka dot pattern.
- Bronze Cory – One of the first cory cats in the industry, and still a favorite.
- Albino Cory – A type of bronze cory with a unique appearance.
- Peppered Cory – Another old timer that’s been known and loved for decades.
- Panda Cory – A small to medium cory with a mask like a raccoon and a lovely personality.
- Pygmy Cory – All the cory cat charm and personality in a tiny, tiny package.
If you’re new to cory cats, Bronze and Peppered corys are a perfect choice. They’ve been around for a long time, and have fantastic adaptability.
Appearance and Color
The cory catfish are small, stout fish with an armor-plated appearance. They look this way because they are, in fact, armored. Their scales have adapted and hardened to form an overlapping shield that protects them from most minor external injuries.
Their shape is reminiscent of a torpedo or pyramid, starting with a broad head and tapering down to a narrow table.
They have short barbels (whiskers), compared to many other catfish. However, their barbels are incredibly sensitive and help them to sift through the tank substrate to find food.
Considering that there are hundreds of different species in this genus, it’s hard to narrow down the color. Generally, they have a base color that’s some sort of grayish-silver or brown. The colors of the upper scales, and patterns can differ significantly. For instance:
Bronze Corydoras, C. aeneas – A light brown cory cat with vibrant dark green bands down the sides. The face is intensely silvery.
Albino Corydoras, C. aeneas – The albino version of the bronze cory, completely lacking in coloration. It’s a ple pinkish-white with pink eyes.
Peppered Corydoras, C. paleatus – A silvery-brown corydoras peppered with greenish-black spots ranging from the anal fin, to just behind the fish’s face.
Panda Corydoras, C. panda – A beautiful, tan corydoras with a black dorsal fin, and black bands across the eye and the base of the tail. The bandit corydoras, C. metae, is similar, but has a black band that extends from the base of the tail to the dorsal fin.
Sterbai Corydoras, C. sterbai – a silver-brown cory with a golden tinge to its belly and the base of some fins. It’s entirely covered in uniform rows of dark brown or black spots.
Julii’s Corydoras, C. julii – Light silver with a black patch on the dorsal fin, two horizontal black bands, and many black spots and stripes. – Light silver with a black patch on the dorsal fin, two horizontal black bands, and many black spots and stripes.
Temperament and Compatibility
Cory catfish are some of the most peaceful bottom-dwellers you’re likely to encounter. Unlike many other catfish, they rarely show any territorial tendencies. If territoriality does occur, it’s usually towards others of their kind.
If they happen to become territorial, it usually involves some chasing. However, they’re unlikely to injure one another or the rest of the tank’s inhabitants.
It’s best to keep at list six cory cats.
Cory catfish should always have other companions of their kind. They’re relatively small fish, and easily feel threatened when left by themselves. For best results, try to have at least five or six cory cats. Shoaling behavior will help these fish to feel secure, and will also lessen any territoriality if it arises.
Corydoras Tank Mates
Cory catfish make excellent companions for a wide range of fish. They’re great for incorporating into a community setup with other small fish or a tank with larger, non-aggressive fish.
Some of the excellent choices for mixing with corydoras include:
- Discus and angelfish- The corys’ small size and peaceful nature make them ideal for cohabiting with these fish.
- Tetras – Perfect mid-level fish to go with these peaceful bottom-dwellers.
- Hatchetfish – A relatively peaceful surface-dweller with a similar habitat in the wild.
- Rasboras – Small, unobtrusive fish that fill a different layer of the tank
- Bettas – Since they fill different layers of the water column, and have vastly different colors, these fish will get along perfectly.
- Peaceful dwarf cichlids – Though these fish tend to be bottom dwellers, they’re unlikely to see cory cats as a threat.
There are hundreds of other species that you could keep with your cory cats. Anything small with a peaceful temperament, or larger with a calm nature and small mouth, will do.
Corydoras and Goldfish
One word of warning, though. Even though Corydoras catfish can withstand cool temperatures, you should never mix them with goldfish of any size. Goldfish are notoriously greedy, and they will try to eat your corys.
That’s not only sad because you’ve lost your cory, though. As mentioned before, cory cats are armored. They have sharp ridges on the scales around their gills, to give them an advantage against predators.
However, goldfish will swallow corys whole. When the cory flares its gills in an act of self-preservation, it may get stuck in the goldfish’s throat. Many inexperienced fishkeepers have lost both fish when a goldfish swallowed a cory and the goldfish suffocated on the catfish.
As with most fish, we’d not recommend keeping corys with any fish that might be able to swallow them.
Can You Keep Cory Catfish with Snails?
Absolutely! These fish have little to no problem cohabiting with snails. Bear in mind that, though they may eat snail eggs on occasion, they’re unlikely to keep your snail population in check.
Snails lay their eggs with an almost glue-like coating, and very few fish can eat through it.
Best Corydoras Catfish to Keep with Bettas in Small Tanks
If you’re planning on keeping cory cats with your betta, it’s possible that you only have a 10-gallon aquarium, or even less than that.
Considering that you need five or six corydoras, the best fish for this setup would be:
- Pygmy cory C. pygmaeus
- Tail spot cory C. hastatus
- Salt and pepper cory C. habrosus
- Smudge spot cory C. similis
- Shy cory C. gracilis
If you’re keeping them with a betta in a larger aquarium, almost any species of cory will do. You probably want to avoid the largest species, as they may be slightly intimidating where your betta is concerned.
Buying and Introducing New Cory Catfish
Unlike some fish, corydoras catfish are fairly simple creatures to buy and keep. When you’re shopping for new cory cats, ensure that you’re buying healthy animals by:
- Inspecting the barbels to check for broken barbels or other damage. Their barbels are short but can get damaged, and wounded barbels can get infected. Cory cats also can’t feed properly without their barbels.
- Checking the skin for a slight sheen. Healthy corys always have a slight gloss to their scales, thanks to the mucus layer on their skin. An absent sheen indicates a sick catfish.
- Asking the seller to feed the catfish so you can see if they have a healthy appetite. Corys love to eat and refusing food is a sure sign of disease.
- Checking for any missing scales, broken spines in the fins, and other damage. Any wound may become infected, and broken bones are a serious problem.
If the stock you’re inspecting seems healthy on all these fronts, you can go ahead and purchase them.
Whenever you buy new fish, whether they’re cory catfish or African butterflyfish, you should quarantine them for two weeks. This gives you time to check for any signs of disease or parasites. It will also allow you to treat any stress-induced conditions that pop up.
The quarantine tank should be a separate setup from the one you usually house your fish in. Most aquarists keep a bare-bottom tank with a simple foam or corner filter for this purpose. If you need to change the water due to disease or having to medicate fish, a sparse setup cuts down on things to clean.
Check for any lethargy, absence of appetite, or other common signs of infection or parasites. If, after two weeks, the fish look healthy then you can add them to their new home.
The 20-Minute Float
Whenever you buy new fish or move them from one tank to another, you have to equalize the water temperatures to prevent shocking them. The easiest way to do this is to use a Ziploc bag or a large-mouthed bottle.
Place the fish in the bag or bottle with a couple of cups of water. Enough so the fish can swim freely, but not enough so the bottle sinks. Let it float for twenty minutes so that the water temperature in the jar becomes the same as the water in the tank.
Then, use a small net to remove the fish and place it in the tank. Never pour the water in, to reduce the risk of introducing parasites or diseases.
Cory Catfish Tank Setup
Cory catfish are fairly easy to keep, and not particularly demanding. Below, we’ll take a closer look at their requirements and help you set up their aquarium so you have the happiest cory cats ever.
Corydoras catfish are relatively small animals and don’t require an awful lot of space. However, they prefer to be kept in small shoals of five to six animals.
Bearing this in mind, you should aim at the following tank sizes:
- For dwarf corydoras – 10-gallon aquarium
- For medium-sized corydoras – at least a 20-gallon aquarium
- For large corydoras – 30-gallon aquariums or larger
These catfish are fairly adaptable and can withstand a wide range of conditions. They thrive best in a temperature range of between 72°F and 78°F.
They can live well in many different levels of water hardness. If you want to breed them, or just keep them at their very best, aim for a water hardness of 18 to 220 parts per million.
Cory catfish naturally come from river basins and other bodies of water with a fair amount of decomposing matter. This means that the water is slightly acidic, and they prefer that in captivity as well. Aim for a pH of 7.0 to 8.0.
You can buy test kits and adjustment kits for both hardness and pH at most reputable pet stores and aquarium stockists. You can also acidify the water slightly by using peat moss or coco coir.
Cory catfish naturally occur in bodies of water with a soft, malleable substrate. They also prefer soft, slightly acidic water.
Bearing these things in mind, a layered substrate with sand, peat moss, or soft soil is a good bet. If you’re not planning on planting the aquarium, sand or peat moss will do well as a solo substrate.
Cory catfish don’t particularly need lighting to survive. However, if you want them to truly thrive, it’s best to offer them a day-and-night cycle.
We recommend a full-spectrum globe with a 12-hour on and 12-hour off cycle. This approach will mimic their natural exposure to sunlight. It also allows you to change the “seasonality” of the aquarium by adjusting the lighting hours and the temperature.
Mimicking the change of seasons can be incredibly helpful when you’re trying to induce breeding behavior.
Filtration and Water Flow
Cory catfish naturally come from bodies of water with a high percentage of dissolved oxygen. This is both because of the amount of plant life in these water bodies, and because they’re connected to rapidly flowing bodies of water.
In the aquarium, Corydoras catfish don’t appreciate strong currents. It’s best to try and moderate the flow of water so that it flows closer to the surface of the tank, rather than through the bottom layer.
Undergravel filters are an excellent addition to a tank containing cory cats, but they shouldn’t be too strong. Oversized filters may place unnecessary stress on the catfish since they’d have to struggle against its pull from below.
A large platform filter will work quite well for these fish, but a canister filter is even better. They need significant amounts of oxygen, so the more oxygen you can add the better. To this end, consider planting the tank and adding airstones.
Should You do a Planted Corydoras Tank?
If you can do a planted tank for your cory catfish, then you absolutely should. As mentioned, these fish appreciate high oxygen levels in their tanks. Plants can help to increase and maintain the amount of oxygen present.
What Kinds of Plants Should You Use?
Your cory cats are unlikely to be disruptive towards plants in the aquarium. They aren’t likely to nibble at them either. As a result, you can plant the tank with whatever you like.
From Amazon swords to Cryptocornes, cory catfish appreciate any plant that creates oxygen.
Cory Catfish Feeding
Cory catfish are easy fish to feed. As long as you have a good sinking pellet food, supplemented with fresh greens and live food, they’ll do well.
Some cory cats may eat from the water’s surface, and others will refuse.
Are Corydoras Picky Eaters?
No, cory cats aren’t picky. However, they prefer to eat on the floor. If you’re feeding them vegetables or live foods, ensure that the food sinks. You can easily weigh things like lettuce or spinach down with a heavy pebble.
How Often Should Corydoras Eat?
You should feed your cory catfish as much as they’ll eat in five minutes, once or twice a day.
What Is Corydoras Favorite Food?
Individual groups, species, and even fish may have different favorite foods. Some may prefer bloodworms, while others love tubifex. It’s up to you to get to know your fish and find their favorite meals. Most cory cats love fresh greens and live foods.
Do Corydoras Eat Algae?
Yes! Corydoras love algae, and will generally keep your tank more or less algae-free. If you have an entire shoal of these fish, and the tank’s substrate is still full of algae, you probably have a problem with high nitrates.
As we’ve mentioned above, there are hundreds of species of Corydoras. As you can imagine, that translates into a lot of price diversity.
Common species like the bronze and peppered cory generally cost under $10. However, rare species may cost as much as several hundred dollars.
Corydoras Breeding: What You Need to Know
If you have plans to breed your cory cats, your water conditions need to be optimal. It’s not particularly difficult, in most cases, and many have done it.
Set up a tank with soft water, some acidity, and no other fish. The tank can be as small as 3 gallons generally. You need some kind of soft filtration and some fine-leaved plants for the best results.
The preferred ratio is two males to every female. If the fish are in spawning condition, they’ll often breed without further intervention. If they seem reluctant, reduce the water level over five days, till roughly 40% of the initial volume remains.
On day number six, replace the water you’ve removed with water that’s around 5-10 degrees cooler than the tank water. This replicates the water conditions during the rainy season when cory cats usually spawn in the wild.
If all goes according to plan, the female will lay eggs on the plants or the side of the aquarium and the male will fertilize them. At this point, you can move the adults back to the main aquarium.
Many aquarists like to hatch the eggs in a plastic sieve or fry protector. You can use a razor to carefully remove the eggs from the glass and place them in a sieve. Around 48 hours after spawning, the eggs will hatch. The main advantages of the sieve are that the water below the surface has more oxygen, and it makes it easier to feed the fry.
You can keep them in the sieve for the first five to seven days, then release them into the breeding aquarium till they’re large enough to move without shocking the young fish.
Once the young have absorbed their yolk sacs, usually within 12 to 24 hours, you can start feeding them brine shrimp nauplii. As they grow, introduce water daphnia, cyclops, and other small live foods into their diet. Powdered flake is also excellent as an additional food.
There’s a reason why corydoras catfish have become, and stayed, popular for decades. They’re easy to keep, feed, and sometimes breed. They have wonderful personalities and are entertaining to look at. We’d recommend these catfish for any soft-water community aquarium.
If you have any questions, feel free to contact us and we’ll do our best to get back to you!
About the author
Hi, I’m Johanan! I love animals of all shapes and sizes, but especially fish. I’ve gone from working at a pet store as a teenager to keeping and breeding Bettas and other fish at home. My passion for fish is endless!
You can find my articles here.