Splash tetra

The splash tetra (Copella arnoldi) is a remarkable characiform fish from the lower Amazon Basin in Brazil and the coastal drainages of Guyana, Suriname, and French Guiana. Reaching 4.5–5.5 cm (1.8–2.2 in), it is a slender, surface-dwelling species with an elongated body and an upturned mouth adapted for feeding at the water surface. Males develop longer, more colourful fins with red and black margins, while females remain plainer and rounder when gravid. The species is best known for its extraordinary reproductive behaviour.

Splash tetras require a tank with a large surface area — at least 90 × 30 cm (~80 L / 21 gal) — and a tight-fitting lid, as they are accomplished jumpers. The aquarium should be densely planted with floating plants, overhanging vegetation, driftwood, and dried leaf litter to simulate the blackwater conditions of their native habitat. Dim lighting, gentle surface agitation, and stable water chemistry (pH 4.0–7.5, temperature 20–28°C) are essential. They are sensitive to parameter swings and should only be added to mature tanks.

The splash tetra's breeding strategy is unique among aquarium fish. The pair leaps out of the water together and clings to the underside of an overhanging leaf or the tank cover glass using their pelvic fins, depositing 5–10 eggs per event until 100–200 total eggs are laid. The male then splashes water onto the eggs with his tail every minute for 36–72 hours — day and night — until they hatch and the fry drop into the water. Breeding requires a tank with accessible overhanging surfaces at the correct height. Feed a varied diet of live and frozen foods (Daphnia, Artemia, bloodworm, fruit flies) supplemented with high-quality flake. Keep in groups of 8–10 with peaceful, similarly sized tankmates.