Quick answer: Cory catfish (corydoras) are small, peaceful South American bottom dwellers that grow about 1 to 3 inches (2.5 to 7.5 cm) and often live 5 to 10 years. Keep them in a group of at least 6 of the same species, in a cycled tank of 20 gallons or more for most types (10 gallons works for pygmy and other dwarf corys), at 72 to 78 F (22 to 26 C) and a pH of about 6.5 to 7.8. Give them soft sand or smooth fine gravel and feed sinking food every day. The mistake most people make is buying one or two corys as a “cleanup crew.” Corys don’t live on leftovers, and a lone cory is a stressed cory.
I’ve kept corydoras in my own tanks for years and made several videos about them on my YouTube channel, AQUA PLANET 128. Here’s my care guide video if you’d like to see them in action before you read on:
Cory catfish at a glance
| Detail | Cory catfish |
|---|---|
| Common names | Cory catfish, cory cats, corydoras, corys |
| Family | Callichthyidae (armored catfish) |
| Origin | Rivers, streams and flooded forests of South America |
| Number of species | Over 160 described, plus many unnamed “C-number” types |
| Adult size | About 1 to 3 in (2.5 to 7.5 cm), depending on species |
| Lifespan | Usually 5 to 10 years, sometimes longer |
| Temperature | 72 to 78 F (22 to 26 C) for most species |
| pH | 6.5 to 7.8 (many adapt to 6.0 to 8.0) |
| Hardness | Soft to moderately hard, about 2 to 15 dGH |
| Minimum tank | 20 gal for most species, 10 gal for pygmy and other dwarf corys |
| Group size | 6 or more of the same species |
| Substrate | Sand or smooth, fine gravel |
| Diet | Omnivore: sinking pellets, wafers, frozen and live foods |
| Temperament | Very peaceful |
| Care level | Easy, good for beginners in a cycled tank |
Cory catfish types: which one do you have?
“Cory catfish” covers a huge group of fish, and stores sell many of them under loose names. These are the types you’re most likely to see. Size and temperature matter most when you choose, so check those columns first.
| Type | Adult size | Temperature | Minimum tank | Notes |
|---|---|---|---|---|
| Bronze cory | About 2.5 in | 72 to 78 F | 20 gal | The classic beginner cory, very hardy |
| Albino cory | About 2.5 in | 72 to 78 F | 20 gal | Usually an albino bronze or peppered cory, same care |
| Peppered cory | About 2.5 in | 68 to 75 F | 20 gal | Handles cooler water well |
| Panda cory | About 2 in | 68 to 77 F | 20 gal | Prefers cooler, very clean water |
| Sterbai cory | About 2.5 to 3 in | 75 to 82 F | 20 gal | One of the few that likes warm water, a classic discus tank mate |
| Julii and false julii | About 2 to 2.5 in | 72 to 79 F | 20 gal | Most “julii” in stores are actually the similar false julii (trilineatus) |
| Emerald cory | About 3 to 3.5 in | 72 to 80 F | 30 gal | Larger, metallic green. Technically a close relative (Brochis), not a true cory |
| Pygmy cory | About 0.75 to 1 in | 72 to 79 F | 10 gal | Swims in mid-water groups, great for nano tanks |
| Habrosus and hastatus | About 1 in | 72 to 79 F | 10 gal | Other dwarf corys, often sold alongside pygmies |
A note on the new names. In 2024, a large DNA study (Dias and colleagues, published in the Zoological Journal of the Linnean Society) split the old genus Corydoras into several groups. You may now see the bronze cory listed as Osteogaster aeneus, the panda and peppered corys as Hoplisoma, and the pygmy cory as Gastrodermus pygmaeus. They’re the same fish with the same care. Most stores and hobbyists still just call them corydoras.
Want a quick visual tour of different species? Here’s my top 10 corydoras video:
How big do cory catfish get?
Most cory catfish grow to about 2 to 2.5 inches (5 to 6.5 cm). The full range runs from the pygmy cory at under an inch to the emerald cory at about 3.5 inches. Females are usually a little larger and rounder than males of the same species.
| Size group | Full-grown size | Examples |
|---|---|---|
| Smallest (dwarf) | About 0.75 to 1 in (2 to 2.5 cm) | Pygmy, habrosus, hastatus |
| Medium | About 2 to 2.5 in (5 to 6.5 cm) | Bronze, albino, peppered, panda, julii |
| Large | About 2.5 to 3.5 in (6.5 to 9 cm) | Sterbai, emerald, some long-nosed species |
Store corys are usually sold at about 1 inch and reach adult size in roughly 6 to 12 months with good food and clean water.
How long do cory catfish live?
With stable water and a good diet, cory catfish usually live 5 to 10 years, and well-kept groups sometimes pass that. That makes them one of the longest-lived small community fish. Most corys that die young are lost in the first few weeks, from shipping stress, an uncycled tank or being kept alone.
Why corys need a group, and the honest part about “cleanup crew”
Corys are shoaling fish. In the wild they live in groups of dozens or even hundreds, and in a tank they feel safe only when they have company. A group of 6 or more of the same species is the minimum. Bigger groups are even better. You’ll see more natural behavior: they forage together, rest in a pile and swim in little bursts as a team.
Here’s the part most care guides skip. Corys are sold as “cleanup crew,” and that label gets a lot of them killed. They do sift through the substrate for bits of food, but they don’t eat fish waste, they don’t eat much algae, and a tank’s leftovers are not a diet. A cory that’s expected to live on scraps slowly starves while the other fish eat everything first. Plan to feed your corys on purpose, every day, just like your other fish. If you want help with algae, see our algae eater fish guide instead.
Cory catfish tank setup
Tank size. For a group of 6 bronze, albino, peppered or panda corys, start with a 20 gallon long. Corys use floor space, not height, so a long, low tank beats a tall one of the same volume. Pygmy and other dwarf corys can live in a 10 gallon. Our fish tank sizes chart compares footprints.
Substrate. Fine sand is ideal, because corys love to dig their faces into it and sift. Smooth, rounded fine gravel also works. Here’s an honest point: sharp gravel gets blamed for damaged barbels, but dirty substrate is the more common cause. Bacteria build up in uneaten food and waste, and that’s what irritates their whiskers. Whatever you use, vacuum it regularly.
Plants and cover. Corys like shaded spots to rest. Add driftwood, a cave or two and plants such as anubias, java fern and cryptocorynes. Floating plants dim the light, which helps shy species come out more. Our low light aquarium plants guide has more easy choices.
Filter and flow. A gentle to moderate flow is fine. Corys come from streams with some current, so they don’t need still water, but they shouldn’t be blown around. A sponge filter or a hang-on-back filter works well.
Heater. Most homes need one to keep corys steady in their range. Pick the temperature to suit your species, cooler for panda and peppered corys, warmer for sterbai.
Lid. Corys sometimes dart to the surface to gulp air, and an excited group can jump. A lid prevents losses.
Cycle first. Corys are sensitive to ammonia and nitrite, so only add them to a fully cycled tank. Follow our how to cycle a fish tank guide before you buy.
Water parameters
| Parameter | Ideal range |
|---|---|
| Temperature | 72 to 78 F (22 to 26 C) for most species |
| pH | 6.5 to 7.8 |
| GH | 2 to 15 dGH |
| Ammonia and nitrite | 0 ppm |
| Nitrate | Under 20 ppm |
| Water change | 20 to 25 percent weekly, with a gravel vacuum |
Captive-bred corys handle a wide range of tap water. Wild-caught fish often prefer softer, more acidic water, so ask your store which you’re buying. Stable, clean water matters far more than hitting an exact number.
What do cory catfish eat?
Corys are omnivores that feed on the bottom. Their mouths face downward, so they need food that sinks.
Staples. Good-quality sinking pellets, sinking wafers and granules made for bottom feeders.
Treats. Frozen or live bloodworms, brine shrimp, daphnia and blackworms two or three times a week. These also bring corys into breeding condition.
How to feed. Feed once or twice a day, a little at a time. In a busy community tank, drop food in right after lights-out or spread it to a few spots, so corys get a fair share before faster fish finish it.
How much. Feed what the group can finish in a few minutes. Food left to rot in the sand is the main cause of barbel problems.
Normal cory behavior that worries new owners
Darting to the surface. Corys can breathe air through their gut. A quick dash up for a gulp now and then is normal. Constant trips to the surface can mean low oxygen or poor water, so test and add surface movement if it’s frequent.
“Winking.” Corys roll their eyes down, which looks like a wink. It’s normal and fun to watch.
Lying still on the bottom. Corys rest a lot, often all piled in one spot. A resting cory sits upright and reacts when food appears. A cory lying on its side is a problem.
Swimming up and down the glass. Short bursts are normal, especially after a water change. Nonstop glass surfing can mean stress or poor water.
Cory catfish tank mates
Corys are completely peaceful, so the question is only whether their tank mates will bother them or outcompete them for food.
| Good tank mates | Avoid |
|---|---|
| Neon tetras, black skirt tetras and other peaceful tetras | Large or aggressive cichlids |
| Harlequin rasboras and galaxy rasboras | Goldfish, which prefer cooler water and grow large |
| Honey gouramis | Crayfish and large crabs |
| Guppies, platies and other small livebearers | Big predatory fish that fit corys in their mouths |
| Bristlenose plecos and otocinclus | Very fast, greedy bottom feeders in a small tank |
| Cherry shrimp, Amano shrimp, mystery and nerite snails | Tiger barbs in small tanks, which can harass them |
Corys and bettas. In a tank of 10 gallons or more, many bettas ignore corys, since corys stay on the bottom and bettas stay near the top. Choose a calm betta and have a backup plan. Our betta fish tank guide covers betta tank mates in more detail.
Cory catfish stocking ideas
| Tank | Stocking idea |
|---|---|
| 10 gallon | 8 pygmy corys, 6 chili rasboras or ember tetras, a few cherry shrimp |
| 20 gallon long | 6 bronze or panda corys, 10 neon tetras, 1 honey gourami, 1 nerite snail |
| 29 gallon | 8 peppered or julii corys, 10 harlequin rasboras, 1 bristlenose pleco |
| 40 breeder or 55 gallon | 10 to 12 corys of one species, a large tetra school, a pair of honey gouramis |
Check your plan with our aquarium stocking calculator before you buy.
Male vs female cory catfish
The easiest way to tell is to look down at them from above. Females are larger, with a wider, rounder body behind the pectoral fins, especially when full of eggs. Males are smaller and slimmer. From the side, males often have a more pointed ventral fin, while females have a broader, rounded one.
Breeding cory catfish
Corys are one of the easier catfish to breed, and many keepers find eggs on the glass without even trying.
Setup. Use a group with more males than females, such as 2 males per female. Condition them for a week or two with frozen bloodworms and other rich foods.
The trigger. A large water change with slightly cooler water often sets them off, because it mimics the rainy season in the wild. Males chase the female, and the pair forms a “T-position,” with the male clasping the female’s barbels.
Eggs. The female holds a few eggs between her pelvic fins, then sticks them to the glass, plants or decor. A spawn can produce dozens of eggs over a few hours. The parents don’t guard them and may eat them.
Raising fry. Move the eggs to a separate container or breeder box with water from the tank and gentle aeration. They hatch in about 3 to 5 days. Feed the fry tiny foods like microworms, baby brine shrimp and crushed fry food, and keep the water very clean.
Here’s my step by step video on breeding corydoras:
Common cory catfish problems
Worn or missing barbels. The whiskers look short, red or eroded. Usually caused by dirty substrate, high nitrate or rough gravel. Vacuum the substrate, do extra water changes and switch to sand if your gravel is sharp. Barbels often grow back once conditions improve.
Red gills or red patches. Often a sign of ammonia or nitrite burns or a bacterial infection. Test the water right away and do a water change.
Ich. White spots like grains of salt. Corys are sensitive to many medications and to salt, so use an ich treatment labeled as safe for scaleless and bottom-dwelling fish, and follow the label carefully.
Not eating. New corys are often shy for a few days. Feed after lights-out. If an established cory stops eating, check the water and watch for bloating or white stringy poop.
Sudden deaths after buying. Corys stress easily during transport. Drip acclimate them over an hour and add them to a mature, cycled tank. Corys can release a mild toxin when badly stressed, so avoid crowding many in a small bag or container for long.
Getting stuck in a net. Corys have sharp spines on their fins that snag in nets, and the spines carry a mild venom that can sting. Catch them with a cup or a fine, soft net, and handle them gently.
Is the cory catfish right for you?
Corys are a great choice if you want a peaceful, active bottom group for a community tank of 20 gallons or more, or a nano tank with pygmy corys. They’re hardy, long-lived and endlessly entertaining.
They’re not the right choice if you only want one or two “cleaner” fish, if your tank has sharp, dirty gravel you don’t want to change, or if your tank mates are large cichlids or other fish that could eat them.
FAQ
How big does a cory catfish get?
Most cory catfish grow to about 2 to 2.5 inches (5 to 6.5 cm). Pygmy corys stay under 1 inch, and emerald corys reach about 3.5 inches.
What is the smallest cory catfish?
The pygmy cory, at about 0.75 to 1 inch. Habrosus and hastatus corys are similarly tiny, and all three can live in a 10 gallon tank.
How long do cory catfish live?
Usually 5 to 10 years with clean, stable water and a good diet. Some well-kept groups live even longer.
How many cory catfish should be kept together?
At least 6 of the same species. They’re shoaling fish and feel stressed and hide more in smaller groups.
Can a cory catfish live alone?
It can survive, but it won’t thrive. A single cory is often shy and stressed. Add more of the same species, or rehome it to a tank with a group.
How many cory catfish can go in a 10 gallon tank?
About 6 to 8 pygmy or other dwarf corys. Standard-size corys like bronze or panda corys need at least a 20 gallon long for a group of 6.
Do cory catfish need sand?
Sand is best, but smooth, fine gravel also works. The most important thing is keeping the substrate clean, since dirty substrate damages their barbels.
Do cory catfish eat poop or algae?
No. Corys eat leftover food they find, but they don’t eat fish waste and eat very little algae. Feed them sinking food every day.
How do you care for albino cory catfish?
The same as bronze or peppered corys, since albinos are usually color forms of those species. Keep 6 or more, use sand, keep the water at 72 to 78 F and feed sinking food. Albinos may prefer slightly dimmer light.
Why is my cory catfish swimming to the top?
Occasional trips to gulp air are normal. If corys keep racing to the surface, test for ammonia and nitrite and add more surface movement for oxygen.
Final thoughts
Cory catfish are one of the best fish you can add to a peaceful community tank. Give them a group of 6 or more, a cycled tank with clean sand, a temperature that suits their species and a few sinking meals a day, and they’ll reward you with years of busy, friendly bottom activity. Start with a hardy bronze, albino or peppered group in a 20 gallon long, or a pygmy group in a 10 gallon, and you’ll quickly see why so many fishkeepers end up with corys in every tank. For more easy community fish, see our best aquarium fish for beginners guide.
