Corydoras undulatus

About

Found in the Lower Paraná River basin and coastal river systems of southern Brazil, this small armored catfish, Corydoras undulatus, is one of the more compact members of a genus already known for modest sizing, topping out at around two inches as an adult. Like other corydoras, it is completely peaceful and does well sharing space with similarly sized, non-aggressive tankmates. What sets it apart from many of its cousins is its ability to breathe air facultatively, meaning it can gulp atmospheric oxygen at the surface when dissolved oxygen levels in the water drop low. This adaptation is a holdover from living in environments where water conditions can shift considerably. In the aquarium it still exhibits this behavior from time to time, so seeing it dart to the surface briefly is perfectly normal and not a sign of distress. It is best kept in groups rather than alone, as it is a social animal that tends to be more active and settled when it has companions of its own kind. While peaceful and small enough for a modest-sized tank, it lands in the intermediate care category, partly because it appreciates consistent water quality and a well-maintained setup to thrive over its four-to-five year lifespan.