A school settling onto the bottom
Corydoras are social to their core, and the first weeks of the year set the pattern: a school of six or more of the same species, added to a cycled tank with a soft sand floor, will spend a few days clustered nervously and then begin exploring in twos and threes. Sand matters more than most new owners expect. These catfish sift substrate through their gills and push their whiskered faces into it all day, behaviour that sharp gravel frustrates and can injure. Given sand, cover at the back, and dim corners to rest in, a new school usually turns bold surprisingly quickly.
Feeding them on purpose, not on leftovers
The most persistent myth a first-year owner unlearns is that corydoras live on scraps. They are poor cleaners and enthusiastic eaters who need their own sinking foods reaching the floor: small wafers, granules, and frozen or live worms and similar foods a few times a week. Feed the tank's mid-water fish first or feed the corys after lights dim if quicker tankmates steal everything. Over the year a well-fed school grows noticeably, females becoming rounder than males, and portion control becomes the balance to strike, because an overfed bottom fouls faster than any other layer of the tank.
Behaviour you will learn to read
By mid-year the school's personality is on full display. You will see group foraging lines sweeping the sand, mid-afternoon rest piles where several fish sit motionless together, and the species' trademark blink-like eye movements and gulps of air at the surface, which are normal in moderation. Breeding behaviour sometimes appears in mature, well-fed groups after a cool water change, with pairs pressing together and eggs appearing on glass or leaves, though raising fry is a separate project most first-year keepers simply observe. The real skill you gain is spotting the off day: one fish alone, not joining the forage, is a fish to watch.
Barbel and water-quality watch-outs
A corydoras reads its world through the barbels around its mouth, so worn, shortened barbels are an early warning that the substrate is too sharp or the floor too dirty, and they deserve a same-week response: check the sand, siphon the bottom, and test the water. Because these fish live where waste settles, ammonia and nitrite problems reach them early, showing as lethargy, rapid breathing, or repeated frantic trips to the surface. Regular partial water changes, a filter that is maintained rather than merely present, and restraint with stocking keep the floor layer safe for the fish who live on it.
Closing the year with a confident school
End the first year and a good corydoras school is usually the tank's most reliable entertainment and its best indicator that the bottom is healthy. Keep a note of your species, school size, the sinking foods they favour, and any breeding activity, because a school is a long-term group whose members can live for years. Should the school ever need a new home, KinsLe's Transferrable Profiles passes those corydoras details on with the fish, so their next keeper inherits the group history instead of starting the school from scratch.