Serpae tetra

About this species

The serpae tetra has a red to orange-red body, usually with a dark shoulder mark. Colour and mark shape vary among wild populations and captive strains. Selectively bred forms, including long-fin and balloon forms, are also sold; their altered shapes should not be treated as representative of the standard fish. Current taxonomic sources use Megalamphodus eques (Steindachner, 1882). Hyphessobrycon eques is a familiar older combination; Hyphessobrycon serpae and several historical combinations are treated as synonyms.

Seriously Fish reports about 40 mm standard length, measured without the caudal fin; FishBase also gives approximately 4 cm standard length. The species occurs across parts of the Amazon and Paraguay basins in Brazil, Peru, Bolivia, Paraguay and Argentina. Colour pattern varies by population, and the broad range includes different habitats.

Natural habitat

In nature Megalamphodus eques is usually found in still or sluggish water, including quiet tributaries, ponds and small lakes. Fish aggregate around marginal vegetation and submerged roots. In an aquarium, provide planted or woody shelter around the edges while retaining open swimming space for the shoal. A dark substrate and subdued light may show the colours well, but are not health requirements.

Leaf litter or peat is optional and requires sensible maintenance; neither replaces stable water quality. Use aquarium-safe materials and maintain good oxygen exchange. The species can live in a biotope-style tank or a carefully planned community aquarium.

Aquarium and layout

Seriously Fish gives a minimum aquarium footprint of about 80 × 30 cm, equivalent to roughly 72 litres at a typical water depth. This is a source-based minimum guideline, not a guarantee that every tank of that volume is suitable. A longer aquarium gives the shoal more horizontal room. Keep at least twelve fish; a larger group helps social attention remain within the species and reduces the chance that tankmates become targets.

Place plants and wood along the margins and leave a clear central swimming area. Use a mature filter, regular water changes and flow that allows normal swimming. The source suggests four to five tank turnovers per hour for the minimum footprint. Direct the outlet so that it does not create a strong jet across the whole swimming area. Introduce fish gradually and check that every individual reaches food.

A small group in a cramped tank is not a safe temporary arrangement: space and shoal size are part of the care requirement. Avoid sharp decor and cover the aquarium securely; active tetras may jump when startled.

Water conditions

The specialist care profile gives 20–28 °C, pH 5.0–7.5 and GH 1–15 dGH. These are broad species ranges, not a reason to move quickly between extremes. Captive-bred fish are described as adaptable; mildly acidic to neutral water is a cautious choice for wild fish. FishBase lists partly different ecological values and another temperature range, neither established specifically as an aquarium optimum. We therefore use the explicit aquarium range from Seriously Fish for routine care.

Most important is stability appropriate to the fish’s source. The reviewed sources do not establish a species-specific KH target. Do not add salt: this is a freshwater fish. Measure changes and make them gradually while watching breathing, colour and appetite.

Behaviour and group size

Serpae tetras form loose social groups with hierarchy, and males may display against one another. Their reputation for fin-nipping is real. Seriously Fish notes that it can be more pronounced when too few fish are kept or space is limited. A group of at least twelve is therefore important. A larger shoal still needs observation because individuals and aquarium layout matter.

Choose sturdy, active tankmates of suitable size. Slow, shy or long-finned fish such as some gouramis, angelfish and guppies face greater risk of stress or fin damage. Shared temperature or pH alone does not establish compatibility. Give each group enough room and feed in more than one place when needed. Separate fish if persistent chasing, damaged fins or missed meals occur.

Sex differences are subtle; mature females are generally rounder and slightly larger than males. Colour alone is not a reliable way to determine sex.

Feeding

This is an omnivore. In the wild it eats small invertebrates, crustaceans, insects and plant material. In aquaria, a quality dry food can form the staple, supplemented with small frozen or live foods such as Daphnia, mosquito larvae and bloodworms. Variety is more useful than treating one food as a complete menu.

Fine granules or flakes are practical for a fish around four centimetres long. The linked TetraMin Mini Granules is a small complete food; offer modest portions and check that all fish actually eat it. Add varied animal-based supplemental foods. Remove leftovers to protect water quality. Let appetite and body condition guide feeding, and avoid giving more than the shoal can eat promptly.

Breeding

The serpae tetra is an egg-scatterer with no parental care. Adults may eat the eggs. For controlled breeding, use a separate mature tank with subdued light and fine-leaved plants, a spawning mop or a mesh barrier. Choose a mesh that lets eggs fall beyond the adults’ reach. An air-driven sponge filter reduces the risk of eggs or fry being drawn in.

Seriously Fish describes mildly acidic to neutral water and a temperature near the upper end of the normal care range; after conditioning, a pair or small breeding group may be introduced. Eggs are often noticed the following morning. Newly hatched fry need very small food such as infusoria or suitable fine starter food; add Artemia nauplii only once they are large enough. These are source-based general guidelines, not a guarantee of breeding success. Keep water quality stable and avoid abrupt corrections.