Start the corydoras introduction before the bag opens
A corydoras catfish introduction begins with the tank, not the fish. Before adoption day ends, confirm the aquarium is cycled, the filter is running calmly, and the bottom offers smooth sand or fine rounded substrate. Corydoras sift the substrate with sensitive barbels, the whisker-like feelers around the mouth, and sharp gravel can injure those barbels during the very first hours of exploring.
Dim the tank light and the room light. A corydoras arriving from a dark transport bag into a bright, busy tank will dive for cover and may thrash against decor, so low light is a practical kindness, not decoration.
Acclimate the corydoras slowly, step by step
Temperature comes first for a corydoras catfish on adoption day. Float the sealed bag in the tank for about fifteen to twenty minutes so the water inside matches the tank gradually. Then open the bag, roll the top down so it floats, and add a small cup of tank water every few minutes. This slower mixing matters because shop or rescue water often differs in hardness and pH from home water.
After the bag water has roughly doubled, lift the corydoras out gently with a soft net or your cupped container and lower it in near a plant or cave at the bottom. Discard the bag water down a sink, never into the tank, because it can carry waste built up during transport.
The first hours on the bottom of the tank
A newly introduced corydoras will usually freeze, then make short darts between pieces of cover. That stop-start movement is normal bottom-dweller caution, and occasional quick trips to the surface for a gulp of air are also part of normal corydoras behaviour. Leave the light low for the rest of the day and keep faces and hands away from the glass.
Offer the first food later, once the fish has explored: a small sinking pellet or wafer placed near its shelter after lights dim, since corydoras feed most confidently in low light. Remove uneaten food the next morning. A corydoras that has not eaten on night one but is breathing steadily and exploring is still settling, not failing.
Shelter, company, and substrate checks for a corydoras
Company shapes how a corydoras catfish settles after adoption day. These are group fish that rest and forage together, so a lone corydoras will stay far more hidden than one that arrived with companions. If yours came home alone, plan for a compatible group of the same species once the tank and quarantine thinking allow, rather than expecting confidence from a solitary fish.
Walk the bottom with your eyes each day that first week. Check that no sharp ornament edge sits where the corydoras squeezes through, that the filter intake cannot trap a resting fish, and that tankmates are not outcompeting it at feeding time. Barbels that look shortened or a fish that stops sifting the sand deserve a prompt water test and, if the change continues, advice from an aquatic health professional.
Settling the household around the new corydoras
The people around the tank need an introduction routine too. Agree who feeds the corydoras, who checks the temperature, and who is allowed to tap or clean the glass, which should be nobody during the first days.
Write down what you did on adoption day: acclimation length, first food offered, and where the corydoras chose to hide. Those small notes turn guesswork into care when someone else feeds that evening. KinsLe's Family Sharing can hold that corydoras profile and those first-day notes in one place, so every helper in the home sees the same substrate, feeding, and shelter details.