Corydoras: why a group of at least six and a soft substrate matter
A small, hugely popular bottom-dwelling catfish, the Corydoras is often bought solo or in pairs to "clean up" the tank, when its real needs lie elsewhere. Find our other setup tips in the fish habitat section.
A gregarious fish that suffers alone
Corydoras are a highly social species: a study on Corydoras behaviour showed that social experience during development lastingly shapes their response to threats, a sign of how much the group matters for their wellbeing (research on Google Scholar). In practice, a group of at least six is recommended, ideally eight to ten: below that, the fish stays hidden, stressed and eats poorly.
The substrate, a detail too often overlooked
Corydoras constantly forage the tank floor using sensitive barbels to find food. Angular gravel or coarse sand wears down and injures these barbels, which can be worn away entirely. Choose fine, rounded sand or smooth, small-grain gravel, as we recommend for choosing an aquarium substrate in general.
Tank mates and layout
Corydoras do well in a calm community tank, with low hiding spots (driftwood, broad-leaved plants) to group under during the day. Avoid aggressive or overly fast bottom feeders that outcompete them for food; our notes on community versus species-only aquariums apply here too.
Frequently asked questions
Can you keep a single Corydoras?
It is not recommended: a lone individual stays stressed and inactive. Aim for a group of at least six.
How can I tell if the substrate is hurting my Corydoras?
Shortened, reddened or missing barbels are a direct sign of too-abrasive substrate: change it without delay.
Do Corydoras alone keep the tank clean?
No: they help but never replace regular water changes and gravel vacuuming of the tank floor.
This guide is part of Planète Pets’s Fishkeeping universe. Our advice is general in nature: for any health concern, your veterinarian remains the only reference.