Move the shoal, not single corydoras
Corydoras should travel together as a complete shoal in one smooth-sided container of their own tank water. A single cory caught alone and bagged by itself often spends the journey frantic, while the same fish settled among its groupmates rests on the container floor in a loose huddle. Scoop rather than net wherever possible: corydoras have fine barbels around the mouth that fray on rough surfaces, and their pectoral spines can catch in net mesh and snap when the fish twists. A submerged cup, jug, or specimen container lifted under a resting group is slower to position but far kinder.
Why the group and the barbels decide the method
Corydoras read safety from numbers, and a moving day that splits the shoal across bags removes that signal exactly when the fish need it most. These are also bottom fish that taste their way along the substrate with their barbels, so anything abrasive during capture, from gravel piled in a travel bag to a coarse net, works directly against the organs they feed with. Corys also dart to the surface for a gulp of air, even in good water, so their travel container needs a shallow air space under the lid and must never be filled completely to the brim and sealed.
Catching a scattered shoal without a chase
Withhold food the day before so the travel water stays cleaner. On moving day, take out plants and decor first, lower the water level until the corydoras have far less room to scatter, and let the shoal regroup in a corner before you begin. Work a wide, fine, soft net slowly behind the group while guiding them toward your submerged container with a second net or a gentle hand; short, calm movements catch corys faster than lunging, because a chased shoal splits and hides in every remaining gap. Count the fish into the container against the number you keep, then count again at the new tank, since one overlooked cory in a drained tank is the commonest loss with this species.
The journey for small bottom fish
Set the corydoras' container inside a dark box or insulated bag so light and vibration stay low, and keep it level in the car footwell or a wedged spot where it cannot tip. Corys are small, so their water cools and warms faster than a large tank's volume would; insulate the container on cold or hot days and never leave it in a parked car. For a long drive, a small battery air pump with an airstone helps, but keep the bubbling gentle, since a churning container exhausts bottom fish that want to rest. Pack their filter media wet in tank water so the new setup keeps its established bacteria.
Release and the first days after
Build the new tank's bottom before the corydoras arrive, with sand or smooth substrate in place and hiding spots set, because these fish land stressed if they are released onto bare glass with nowhere to settle. Match the container gradually to the new tank's temperature, add small amounts of tank water over time, then lift or tip the shoal in gently and throw the travel water away. Feed lightly the day after, and watch for frayed barbels, redness around the mouth, clamped fins, or a cory sitting apart from the group. Those signs after a move deserve prompt advice from an aquatic veterinarian. Keeping the shoal count, water notes, and moving-day jobs on the corydoras' shared KinsLe Family Sharing profile means whoever unpacks the tank works from the same details you packed it with.