Serpae tetra

Quick facts

Adult size

4.5 cm

Lifespan

can live up to 5 years; 3-5 years

Tank zone

mid

Temperament

semi-aggressive

Difficulty

beginner

Schooling

recommended 8+ (critical minimum 5, thrives at 12+)

Water parameters

Temperature

22–27°C

pH

5.0 to 7.5

Hardness

1 to 15 dGH

Tank requirements

Minimum volume

75 L

Minimum length

60 cm

Flow

low

Lighting

dim preferred

Substrate

any

Driftwood

preferred

Hiding spots

needed

Open swimming room

needed

Feeding

Diet: omnivore, feeds primarily at the mid.

Omnivore, eats everything. Flake, pellets, frozen bloodworm, frozen brine shrimp, frozen daphnia, live food. Feeds in the midwater column. Aggressive feeders that outcompete slower species. Feed twice daily. A varied diet with frozen food maintains the deep red body color.

Compatibility

• Fin-nipper. Not as aggressive as tiger barbs, but persistent enough to shred long-finned fish over time. Bettas, angelfish, and fancy guppies are not safe tankmates.
• Keep in groups of 8+ to contain the aggression within the school. In small groups (under 6), serpae tetras redirect their nipping outward and become a menace to everything else in the tank.
• Best with other robust, fast fish that can handle the occasional chase: larger tetras, barbs, rainbowfish, and catfish. Other semi-aggressive species that can hold their own.
• The deep red body coloring makes them one of the most visually striking tetras available, which is why they keep getting recommended despite the behavioral baggage.

Habitat

Native to the Amazon basin in Brazil, Bolivia, and Paraguay. Found in slow-moving tributaries, backwaters, and floodplain lakes with dense vegetation. The species has been in the hobby since the 1930s. The body is deep red to blood-red with a characteristic black comma-shaped marking behind the gill cover and black-tipped fins. The anal fin has a prominent black edge bordered by white. Under good conditions, the red is intense and saturated. Color fades in stressed fish or fish kept in bright, unplanted tanks. A long-finned variant exists but is somewhat ironic given that the standard form nips fins. Adults reach 4–5 cm. Males are slimmer and slightly more intensely colored than females. Tank-bred universally; wild-caught specimens are uncommon in the modern trade.

Breeding

Egg scatterer, standard tetra breeding protocol. Condition pairs with frozen food. Breeding tank with soft, acidic water (pH 6.0-6.5), dim lighting, and fine-leaved plants. Temperature at 26–27°C. Spawning occurs at dawn. The pair scatters 200-300 eggs among plants. Eggs are light-sensitive. Remove adults after spawning. Eggs hatch in 24-36 hours. Fry need infusoria for the first few days, then baby brine shrimp. Growth is moderate. The species breeds readily in home setups; the difficulty is average for an egg-scattering tetra.

Common problems

Fin nipping is the defining issue and the reason experienced keepers either love or avoid them. In the right setup (large group, robust tankmates, plenty of space), serpae tetras are stunning and mostly well-behaved. In the wrong setup (small group, slow tankmates, cramped tank), they're destructive. Health-wise, they're tough. Ich in new purchases is the standard risk. Columnaris can occur in degraded water. The species is otherwise hardy and long-lived (5-7 years). A common frustration: the red coloring that looked so vivid in the store fades at home because the store used colored background lighting. In a home tank with natural lighting, serpaes still look good but not quite as dramatically red.

Bioload

Bioload coefficient: 1.3 (stockier than neon tetra; slightly higher waste per fish).

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

• How to cycle a fish tank
• Stocking ideas by tank size