Corydoras, or "cory cats," are small armored catfish that spend their days sifting through the substrate in busy little groups. They are peaceful, hardy once settled and endlessly entertaining, but they are not just cleaners. They need their own food and the right substrate.
| Adult size | 1–3 inches depending on species |
|---|---|
| Group size | 6 or more of the same species |
| Minimum tank | 20 gallons for most species |
| Temperature | 72–79°F for most species |
| pH | 6.0–7.5 |
| Substrate | Sand or smooth, rounded gravel |
| Lifespan | 5+ years, often longer |
| Temperament | Peaceful |
Why group size matters
Corydoras are shoaling fish. A single cory often hides and stresses; a group of six or more of the same species moves, feeds and rests together. Different species will mix, but each fish is most confident with its own kind.
Substrate: protect their barbels
Corys find food with sensitive whiskers called barbels. Sharp gravel and dirty substrate can wear them down. Sand is best; smooth, rounded gravel is fine. Vacuum the substrate regularly so waste doesn't build up where they feed. See our sand and substrates.
Feeding
Feed sinking food once or twice a day, making sure some reaches the bottom past faster fish. Good options: Fluval Bug Bites Bottom Feeder Formula, sinking wafers and frozen bloodworms or brine shrimp as treats. Feeding just after lights-out works well since corys are most active at dusk.
Water and behavior
- Keep water clean and well oxygenated, with weekly 20–30% changes.
- Darting to the surface for a gulp of air now and then is normal: corys can breathe air through their gut.
- Constant surface gulping, red gills or lying on their side are signs of poor water quality.
Popular species we carry
- Emerald green corydoras: a larger, shimmering green cory that stays active in groups
- Julii corydoras: spotted and striped, a classic community fish
- Corydoras loxozonus: a smaller species with a bold diagonal stripe
Tankmates
Corys get along with almost any peaceful community fish: tetras, rasboras, gouramis, livebearers, plecos and dwarf cichlids. Avoid large cichlids and fish that pick at bottom-dwellers.
Medication caution
Corys can be sensitive to some medications and to aquarium salt. Use half doses where a label allows it for sensitive fish, and remove carbon only when the treatment says to.
Frequently asked questions
Do corydoras clean the tank?
They eat leftover food on the bottom, but they do not eat waste or algae. They need their own sinking food every day.
Can corydoras live with bettas?
Yes, they are a common and good match in a 10-gallon or larger tank.
Why are my corydoras swimming up and down the glass?
Brief "glass surfing" is normal play, especially in new tanks. Constant frantic swimming can mean poor water quality.
Do corydoras need a heater?
Most species do best at 72–79°F, so a heater is recommended in most homes.
Shop for this guide
- Emerald Green Corydoras
- Corydoras Julii
- Corydoras Loxozonus
- Corydoras and catfish
- Sand and substrates
Questions? Call us at 786-642-3001 or visit the store at 8338 West State Road 84, Davie, FL (Wednesday to Sunday, 12–7 p.m.).