The short answer
Keep corydoras in a group of at least 6, all the same species where you can. Corydoras are social, shoaling catfish, so bigger same-species groups make them bold, active and playful. Two or three left alone become shy and spend the day hidden. Give a group of 6+ a soft or smooth substrate and they’ll forage together across the bottom.
Why the group size matters
Corydoras take their cues from each other — they feed, rest and dash to the surface for air as a group. In too small a number they lose that confidence, stay tucked away and show far less of their charming, busy behaviour. A proper shoal of six or more brings them out into the open and lets you actually enjoy them.
Giving the group what it needs
Corydoras do best with:
- Numbers — 6 or more of the same species
- A soft, smooth substrate to protect their barbels
- Peaceful tankmates on the upper levels
- Sinking food so they get their share, not just the leftovers
They appreciate mature, well-oxygenated water and gentle flow. A 60 litre tank suits dwarf or pygmy species; larger corydoras want more floor space.
Before you add them
Add corydoras only to a fully cycled aquarium, and acclimate them gently. Keep up regular water changes and feed a proper sinking food so bottom feeders aren’t left out. For stocking by tank size, see how many fish in a 60 litre tank, and for another schooler read how many neon tetras to keep together.