Activity for a corydoras starts at the floor
A corydoras experiences the world through its barbels and snout, pushing into the substrate and sifting mouthfuls of sand for anything edible. When the floor is right, a group spends the day on the move: sifting, shoaling in loose formation, resting together, then sifting again. When it is wrong — bare glass, coarse sharp gravel, food that lands in one spot — the same fish sit motionless for hours. Enrichment for this species is mostly about rebuilding the riverbed they evolved to work.
Soft sand is equipment, not decoration
Fine, smooth sand lets corydoras bury their snouts to the eyes and blow the grains out through their gills, which is the behaviour you are trying to unlock. Coarse or sharp gravel locks food down out of reach and gradually wears the barbels they navigate with. If your tank has gravel, even a shallow sand 'beach' across the front, a few centimetres deep, gives the group a working foraging patch — and they will find it within the day and use it constantly. Scatter their food across that sand rather than the gravel, and every meal becomes a search.
A bigger shoal is the strongest enrichment of all
Corydoras are schooling fish that read safety from numbers. A pair hides; six explore; ten or more cruise the tank in the open, performing the loose synchronised laps and glass-side dances keepers love. If your group is small, adding more of the same species will do more for activity than any ornament. Matching species matters — a mixed handful of different cory types shoals loosely at best, while a single-species group moves as one body.
Cover behind, open sand in front
The trick that gets bottom fish out in the open is giving them a covered retreat they trust. Driftwood arches, smooth rounded stone caves and plant thickets along the back and sides, with open sand in front, means a startled cory is never more than a flick from shelter — so it forages in view instead of living under the wood. A few dried leaves along the edges add both cover and a biofilm edge the group will work along in the evenings.
Feed like they forage, and watch the barbels
Break sinking wafers into fragments and spread them after lights dim, when corydoras naturally feed; rotate in frozen daphnia or similar small foods a couple of times a week, thawed and scattered. Uneaten food left in sand fouls quickly, so siphon the foraging patch lightly at water changes. Shortened, reddened barbels, a fish isolating itself, or a whole group gone lethargic are early warnings — check ammonia and the sharpness of the substrate first, and if barbels look eroded or a fish stops feeding altogether, seek advice from an aquatic veterinarian. Rotation of these small jobs is easy to share: KinsLe's Care Teams can put the dusk scatter-feed and weekly sand siphon on a family rota, every completed task stamped with its time.