Madagascar Rainbowfish

The Madagascar Rainbowfish (Bedotia geayi) is a freshwater species endemic to eastern Madagascar, belonging to the family Bedotiidae, a small rainbowfish-related family found only on that island. It is the best-known member of its genus and one of the most commonly kept Malagasy fish in the aquarium trade, prized for its slender silhouette and striking fin patterning. Wild populations face pressure from deforestation-driven habitat degradation and competition from introduced species, and several close Bedotia relatives are considered threatened, making this genus a conservation focus for Madagascar's freshwater biodiversity. Taxonomically it sits within Atheriniformes alongside true rainbowfishes and silversides, though Bedotiidae evolved in isolation on Madagascar.

Bedotia geayi is a slim, torpedo-shaped fish reaching about 10 cm.

• Body: silvery-olive with a subtle dark horizontal stripe running along the midline
• Fins: forked tail with a black outer margin and bright yellow-orange central band; dorsal and anal fins similarly black-edged
• Two separate dorsal fins, a rainbowfish-family trait
• Head: pointed, with large eyes Males show more vivid yellow-red fin coloration and longer fin extensions than females, which appear paler and more rounded-bodied. It differs from Australasian rainbowfishes by its more elongated shape and restricted Madagascar origin.

Madagascar Rainbowfish inhabit clear, well-oxygenated forest streams and rivers along Madagascar's humid eastern escarpment, typically over sand, gravel, or leaf-litter substrates beneath rainforest canopy. Water is generally soft, slightly acidic to neutral, and warm (22-26°C), with moderate current in flowing stretches and calmer pools near banks. The species prefers areas with overhanging vegetation and submerged roots offering shelter and feeding grounds for invertebrates. Its range is restricted to eastern Madagascar's river systems, an area experiencing significant deforestation, which reduces water quality and shading in many catchments. It is largely absent from brackish or standing swamp waters, favoring flowing freshwater habitats instead.

Madagascar Rainbowfish form loose, active shoals that swim in the mid to upper water column, foraging throughout the day on small aquatic insects, crustaceans, algae, and plant debris. Males display mild territoriality around favored spawning sites, flaring fins and intensifying color to court females rather than engaging in serious fighting. Spawning occurs repeatedly over an extended period, with females releasing adhesive eggs among fine plant roots or vegetation, receiving no further parental care. Fry hatch within about a week and immediately begin feeding on microscopic organisms. As opportunistic omnivores, they play a role in controlling invertebrate populations within their stream ecosystems and serve as prey for larger fish and wading birds.