Serpae tetra

Water parameters

Tolerated range for this species. Aim for the middle of each band rather than the extremes.

Tank and habitat

Substrate: any.

Behavior

Plant interaction: plant safe.

Feeding

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.

Origin and habitat

Hyphessobrycon eques, the serpae tetra, is a deep-red characin with an enormous natural range, spread through much of the Amazon drainage in Brazil, Peru, and Bolivia and the Paraguay basin into Paraguay and northern Argentina, the two systems linked through the Guapore. Steindachner described it in 1882. It is best understood as a species complex, and several familiar names, including H. serpae and H. callistus, are now junior synonyms of H. eques. It lives in slow or still backwaters, ponds, and flooded forest among dense plants, leaf litter, and submerged wood. The genus name means roughly of lesser stature and the species name means horseman. The body is deep red to reddish-brown with a dark comma-shaped mark just behind the gill cover and a bold black dorsal fin, and a long-finned form is bred for the trade. It reaches about 4 cm. Its placement is in some flux, like other Hyphessobrycon: some references keep it in the family Characidae, while recent characin revisions move parts of the genus into Acestrorhamphidae.

Breeding

A standard egg-scattering tetra, of about average difficulty. A conditioned pair spawns at first light in a dim, separate tank with very soft, acidic water and fine-leaved plants or a spawning mop, scattering a couple of hundred light-sensitive eggs. The adults are keen egg-eaters, so they should come out once spawning is done. The eggs hatch in a day or so, and the fry need infusoria-grade food before moving to baby brine shrimp. It breeds readily enough in a dedicated setup.

Common problems

Fin-nipping is the defining issue and the reason keepers either rate or avoid the fish. Kept in a proper group of ten or more in a roomy, well-decorated tank with robust tankmates, serpae tetras are striking and mostly behave; kept in small numbers, in tight quarters, or with slow long-finned fish like angelfish and bettas, they turn destructive. Health-wise they are tough, with ich on new fish the usual risk and columnaris only in poor water. One common letdown is colour: the intense red seen in shops is often exaggerated by coloured tank lighting, so under ordinary light at home the fish look good but a little less fiery.

Bioload

Further reading

• The schooling number matters more than you think
• Stocking ideas by tank size