The Right Corydoras Depends on Group Size, Footprint, and Gentle Conditions
Different Corydoras species vary in size and temperature preference, but most do best in groups, on soft or smooth substrate, with gentle tankmates and regular maintenance.
What usually matters most for cory success
Cory choice factor
| Cory choice factor | Safer direction | Why it helps | Common mistake |
|---|---|---|---|
| Species size | Match the species to tank footprint and stocking plan | Larger species need more room to school naturally | Choosing by store availability alone |
| Substrate | Use sand or very smooth gravel | Protects barbels and encourages natural sifting | Sharp gravel that can wear mouths down |
| Social needs | Keep a real group of the same or very similar cory type | Reduces stress and improves activity | Buying only two because they seem quiet |
| Community role | Pair with calm midwater fish | Lets them forage without harassment | Mixing with aggressive bottom competitors |
Corydoras care checklist
| Plan for a proper group rather than a single 'cleanup fish' | |
| Offer hiding cover but keep open bottom area for foraging | |
| Feed sinking foods so faster fish do not monopolize meals | |
| Keep the substrate clean without making it sterile | |
| Treat corys as algae eaters that do not need species-specific care | |
| Use rough substrate because the fish stay near the bottom anyway |
Healthy cory tanks look calm, busy, and social: the fish sift together, rest together, and do not spend the day hiding from flow, crowding, or abrasive decor.
Worn barbels, frantic dashing, chronic hiding, or constant surface rushing point to stress from water quality, rough substrate, unsuitable tankmates, or too-small groups.
Corydoras catfish are small South American bottom-dwellers -- 1--3 inches depending on species -- that are social, peaceful, and one of the best options for community tank substrate cleaning. Over 160 species are described, ranging from the common Bronze Cory (C. aeneus) and Peppered Cory (C. paleatus) to the sought-after Panda Cory (C. panda) and Sterbai Cory (C. sterbai). All require groups of 6+, sand or smooth gravel substrate, clean water, and are incompatible with salt in the water.
| Species | Adult Size | Temperature | Notes |
|---|---|---|---|
| C. aeneus (Bronze) | 2.5 in | 72–78°F | Most available; hardiest beginner cory |
| C. sterbai (Sterbai) | 2.5 in | 77–84°F | Warm water; only cory compatible with discus |
| C. panda (Panda) | 1.5 in | 68–76°F | Cooler water; smaller; schooling |
| C. paleatus (Peppered) | 2.5 in | 68–75°F | Cool water; temperate rooms; active |
Why Groups of 6+ Matter
Corydoras are schooling fish that feel exposed when alone or in pairs. A single cory or a pair will spend most time hiding, stressed, and prone to disease. Groups of 6 produce the natural schooling behavior -- synchronized movement, foraging in groups, playful chasing -- that makes them interesting tankmates. Larger groups of 10--12 in appropriate tank sizes show even more pronounced social behavior.
Species for Different Water Temperatures
Most common Corydoras species prefer 72--78 degrees F -- standard community temperature. Exceptions matter: Sterbai Cory (C. sterbai) tolerates 77--84 degrees F and is one of the only Corydoras compatible with discus tanks. Peppered Cory (C. paleatus) and Bronze Cory (C. aeneus) prefer cooler 68--75 degrees F and do not thrive in warm tropical setups. Panda Cory (C. panda) also prefers cooler water at 68--76 degrees F. Match species to tank temperature before mixing with other fish.
Substrate Requirements
Corydoras have sensitive barbels (sensory whiskers around the mouth) that are damaged by sharp gravel. Eroded barbels impair feeding ability and make animals prone to bacterial infection. Use fine sand (pool filter sand, play sand, or aquarium sand) or smooth round pebbles. Never use sharp or angular gravel substrate in a Corydoras tank. If barbel erosion has already occurred, switch to sand and maintain pristine water quality -- barbels can regrow in good conditions.
Feeding
Corydoras are omnivores that forage the substrate. Sinking pellets (Hikari Sinking Wafers, Omega One Sinking Pellets) and sinking tablets ensure they receive food before surface and mid-water feeders eat it all. Supplement with blanched vegetables (zucchini, spinach), frozen bloodworms, and daphnia. They also consume uneaten food and decomposing plant matter, reducing waste accumulation -- but should not be relied on as the sole cleaning mechanism.
Breeding
Corydoras are among the easiest catfish to breed. Trigger spawning with a 10-degree F water temperature drop simulating rain season, followed by water quality improvement. Females carry 2--4 eggs at a time to surfaces they have cleaned with their mouths; spawning continues for several hours with male fertilizing externally. Eggs are sticky and attach to glass and plants. Remove to a separate rearing tank or protect from adult predation with a mesh divider.
Corydoras species descriptions and husbandry from Sterba (1987) and the Corydoras World database (corydoras.com). Barbel erosion documentation from published aquarium science literature. Breeding behavior from established freshwater fishkeeping resources.