Corydoras Care Hub: Bottom-Dweller Basics and Group Needs
Corydoras are peaceful, social bottom-dwellers that need soft sand, a real group of their own kind and food that actually reaches the floor. This hub covers substrate, group size, feeding, water and the barbel and behaviour checks that tell you your cories are thriving.
Quick answer
Corydoras ("cories") are small, peaceful catfish that live on the bottom and must be kept in groups of at least six of the same species. Give them a soft sand substrate, sinking food that reaches the floor, a cycled tank around 22–26°C and clean, stable water. They are hardy and charming, but they are not tank cleaners — they need feeding like any other fish.
Corydoras are peaceful, social bottom-dwellers that need soft sand, a real group of their own kind and food that actually reaches the floor.
Substrate: why sand matters
Corydoras forage by sifting the substrate with delicate sensory barbels ("whiskers"). On sharp or dirty gravel, those barbels wear down and can become infected and eroded — a common, avoidable problem. Use fine, smooth sand or very rounded fine gravel, and keep it clean. Healthy cories will constantly "dig" and sift, which is exactly the behaviour you want to see.
Fine sand protects a cory's delicate barbels — sharp gravel can wear them down and cause infection.
Group needs
Cories are social shoaling fish. Kept singly or in pairs they become withdrawn and inactive; in a group of six or more of the same species they forage together, rest in piles and show real personality. Mixing several different cory species in small numbers is not the same — each species does best with its own kind, so build a proper group of one type where you can.
Corydoras are social — a group of six or more of the same species is far more confident and active.
Feeding a bottom-dweller
Because cories feed on the floor, food must actually reach them. In a busy community tank, fast mid-water fish often eat everything before it sinks. Use sinking pellets, wafers and tablets, plus frozen or live bloodworm, daphnia and brine shrimp. Feed after lights-out or in a quiet corner if faster fish outcompete them. Never assume they will "clean up" leftovers — that myth leaves cories slowly starving.
Water and tank mates
Keep ammonia and nitrite at 0 and nitrate low with weekly water changes. Cories prefer soft to moderate, neutral water and appreciate gentle flow and good oxygenation. They are perfect community fish with tetras, rasboras, guppies and dwarf shrimp. Avoid large or aggressive tank mates, and never keep them in tanks treated with copper-based or high-salt medications without checking — scaleless catfish are sensitive to some treatments.
Quick FAQs
Do corydoras clean the tank? No. They forage for leftover and sinking food but they do not remove algae or waste, and they must be fed their own food to stay healthy.
How many corydoras should I keep? At least six of the same species. Bigger single-species groups are more active, confident and natural.
Why does my cory dart to the surface? Cories can gulp air from the surface and absorb oxygen through their gut — an occasional quick dash is normal. Constant, frantic surface-gasping is not, and points to a water problem.
Can I use gravel instead of sand? Fine, smooth, rounded gravel can work, but sharp gravel damages their barbels. Soft sand is the safest choice for their natural sifting behaviour.