Catch corydoras with a smooth tub rather than a net, guiding each fish in and lifting the water around it, because their fin spines lock upright and snag in mesh. A corydoras tangled by a pectoral or dorsal spine twists as it is freed, and that struggle tears fin tissue and can bend or break the spine itself. Their barbels, the whiskers around the mouth that taste the substrate for food, are equally delicate: rough surfaces, grit and squeezing damage them, and shortened barbels leave the fish less able to feed well afterwards.
Catching Without a Net
Lower a small, smooth-walled tub into the tank and let it fill. Guide the corydoras towards it with a second container or a slow hand behind the fish, and let it swim in rather than chasing it around decor. Work in brief attempts with pauses, rather than one long pursuit that exhausts the group.
Lift the tub with the fish in its own water and pour gently into the travelling bag or container. Count fish out of the tank and into the container as you go, so none is left stranded in a corner of a tub or in water you are about to discard. Keep your hands wet for any contact, and never lift one by hand in open air, where a startled fish raises its spines.
Bagging for the Journey
Put only a few fish in each bag, so fins and spines are not pressed against tank mates for the whole trip and the oxygen in that bag is shared by fewer bodies. Use tank water, not fresh tap water, so temperature and chemistry in transit match the water the fish left. Because raised spines can puncture a thin bag, a rigid, lidded, smooth container is the safer vessel for a short journey, and a sturdy bag, supported upright so it cannot roll or fold onto the fish, suits a longer one.
Set bags or containers level in a dark box, packed around so nothing slides when the vehicle brakes or turns. Darkness settles corydoras, which are bottom fish used to subdued light, and level packing keeps the water depth even over them rather than sloshing them against the sides. Keep the box away from heaters, cold windows and direct sun, and aim for a steady temperature close to the tank's, since a small volume of water changes temperature far faster than the aquarium did.
Keeping the Trip Short and Steady
Plan the route so the fish spend as little time in transit as you reasonably can, and avoid leaving the box in a parked vehicle while you do other errands. Check once, quietly, rather than opening bags repeatedly; each opening loses warmth, admits bright light and risks a spill. If a bag leaks or a fish is lying on its side and unresponsive to gentle movement of the bag, that fish needs to reach destination water promptly rather than waiting for a more convenient moment at the end of the trip.
Arrival Without a Second Netting
Float the closed bag or set the closed container beside the new tank briefly if the temperatures feel different, then open it in dim light. Lift each fish out in the smooth tub with some of its travelling water and lower it into the tank, rather than netting it for a second time at the moment it is already stressed. Discard the travelling water instead of pouring it into the tank, since it carries waste produced in transit and water from another system if the fish are new arrivals.
Watch the group for the next hour: barbels should be busy against the substrate once the fish explore, and fins should sit unclamped. Offer a small feed only once they are rooting around normally, and note any fish with a torn fin. If someone is receiving the fish for you, KinsLe lets your Care Pass carry the tub-not-net rule and the dim-light arrival steps, so the second handling follows the same care as the first.