Corydoras get bored at the bottom of the tank
Corydoras catfish live through their barbels and their noses, working the substrate for food and information all day, so their boredom shows up as a shoal that sits parked in one corner doing nothing between feeds. A weekly enrichment rotation for corydoras is really a rotation of the bottom of the tank: what there is to sift, where food hides, which shelters stand where, and how the water moves across the floor. Change one element each week and the shoal re-maps its world every time, which for a bottom fish is a full programme of entertainment. Keep the shoal itself constant through every rotation, because for corydoras the group is the enrichment everything else hangs off.
Week one and two: new ground to sift and new shelters
Start the rotation with the substrate itself. In week one, add a defined patch of fine sand in one area of the tank, a shallow tray or a cleared corner filled deeper than the rest, and watch the shoal descend on it: corydoras push their snouts in up to the eyes and sift with obvious enthusiasm, and a fresh patch is investigated for days. In week two, rearrange the bottom furniture: swap the positions of caves, coconut huts, and driftwood, exchange one shelter for a different shape, and add a small pile of smooth pebbles to nose through. Moving shelters resets the shoal's resting map and sends them on a group tour of the new layout. Rinse new items, avoid anything with sharp rims that could damage barbels, and keep at least one familiar shelter in place so the shoal always has a known bolt-hole.
Week three: food hidden like a job of work
Foraging week is the corydoras favourite, because it pays them in their own currency. Instead of dropping the shoal's sinking food in the usual spot, spread it: push a few wafers or pellets partway into the sand patch so the fish have to excavate, scatter small foods across a wide area of floor so the group spreads out to hunt, and tuck one portion under a piece of driftwood. Rotate the food types across the week as well, alternating the staple with frozen bloodworm or daphnia allowed to sink and small softened pellets, so everything that reaches the bottom arrives intact and worth digging for. Keep total amounts the same as usual; the enrichment is in the searching, not the quantity.
Week four: current, leaf litter, and a change of scene
The fourth week changes how the tank floor feels and flows. Add a layer of dried botanical leaves, such as Indian almond leaves, across one area: corydoras nose through leaf litter endlessly, grazing the biofilm that grows on it, and the litter doubles as extra cover for a shy shoal. Adjust the filter outflow or add a gentle air stone at the opposite end of the tank so a new lane of current crosses the bottom, and the shoal will surf it, regroup in it, and rest at its edges. Remove spent leaves as they soften to mush, and count this week's water check as part of the rotation, since botanicals and buried food both ask a little more of the filter.
Running the rotation as a household rota
Corydoras enrichment lapses quietly because the fish are undemanding, and the first sign of a lapsed rotation is a shoal that has gone back to sitting in its corner. Tie the weekly swap to the water-change day, write the four-week cycle where the fish food lives, and jot one line each week about what the shoal actually did with the change: how long the sand patch stayed busy, which shelter won the pile-up. In KinsLe, Care Teams lets you assign each week's corydoras rotation task to a named family member and mark it finished with a timestamp, so the shoal's floor stays interesting even when one person is away.