Bronze cory

Quick facts

Adult size

7 cm

Lifespan

can live up to 15 years; captive average 5-10 years; well-cared-for specimens routinely hit 10+

Tank zone

bottom

Temperament

peaceful

Difficulty

beginner

Schooling

recommended 6+ (critical minimum 4, thrives at 8+)

Water parameters

Temperature

22–28°C

pH

6.0 to 7.8

Hardness

2 to 25 dGH

Tank requirements

Minimum volume

90 L

Minimum length

75 cm

Flow

low

Lighting

moderate

Substrate

sand required

Driftwood

preferred

Hiding spots

needed

Feeding

Diet: omnivore, feeds primarily at the bottom.

Sinking pellets, sinking wafer fragments, and frozen bloodworm or brine shrimp. Corys are not effective tank cleaners despite the myth; they need direct feeding. They sift through substrate with their barbels, so sand is strongly preferred over gravel. Sharp gravel wears down and damages barbels, leading to bacterial infections. Feed in the evening or after lights-out when the corys are most active. Corys are slow, methodical eaters and will lose out to faster midwater fish at feeding time.

Compatibility

• Peaceful with everything. One of the safest community fish available.
• Pairs well with tetras, rasboras, livebearers, gouramis, and other non-aggressive species.
• Keep in groups of 6+ of the same species. Corys school by species; mixing bronze and panda corys doesn't satisfy the schooling need for either.
• Safe with shrimp and snails. Too small-mouthed to eat even baby shrimp.
• Avoid housing with aggressive cichlids or large fish that might harass bottom-dwellers.

Habitat

Native to shallow, slow-moving streams and flooded areas across South America, from Trinidad to the Rio de la Plata. One of the first tropical fish imported for the hobby (late 1800s) and still one of the most common corydoras in the trade. Sold in multiple color forms: wild-type bronze, albino (pale yellow-pink with red eyes), and green (darker olive). All are the same species and interbreed freely. Social bottom-dwellers that spend their time sifting through substrate for food particles using their sensitive barbels. They breathe atmospheric air by gulping at the surface, which is normal behavior, not a sign of low oxygen.

Breeding

Egg depositor. Breeding is triggered by large cool water changes that simulate the rainy season (replace 50% of tank water with water 2–3°C cooler). The T-position spawning is distinctive: the female cups 2-4 eggs in her pelvic fins, the male fertilizes them, and the female swims away to press the sticky eggs onto a surface (glass, plant leaves, filter intake). This repeats for 1-2 hours, producing 50-200 eggs. Parents ignore the eggs but other fish will eat them. Eggs hatch in 3-5 days. Fry are large enough for crushed dry food and baby brine shrimp from day one. One of the easier egg-laying fish to breed.

Common problems

Barbel erosion from sharp substrate. This is the single most common problem. Sand is the correct substrate for corys; gravel wears down the barbels over months, eventually causing bacterial infection and making it harder for the cory to find food. Red or inflamed barbels are a warning sign. Ich is common in newly purchased fish. Corys are sensitive to salt and many medications; use half-dose treatments and avoid salt entirely. The surface-breathing behavior is normal and not a sign of distress unless it's constant (more than a few times per hour), which may indicate low dissolved oxygen.

Bioload

Bioload coefficient: 2.5 (7 cm bottom dweller with hearty feeding; size formula gives ~2.9, pulled down slightly for omnivore profile).

Bioload coefficients are calibrated against the neon tetra as the anchor (1.0). See the methodology page for the formula and how each value was derived.

Further reading

• Stocking ideas by tank size