Balzanii Eartheater (Rio Parana)

Gymnogeophagus balzanii is the largest species in its genus, inhabiting the Paraná-Paraguay river system across Brazil, Paraguay, and Argentina. It is one of the most sexually dimorphic Gymnogeophagus species: breeding males develop a pronounced, gel-filled nuchal hump and intensely iridescent turquoise-green and orange flank colouration, while females remain smaller and plainer. A delayed mouthbrooder, females hold fry for up to two weeks. The species experiences natural seasonal temperature variation from subtropical cool winters to warm summers, making it suitable for aquaria without constant high heating. Fine sand substrate, open swimming space, and moderate to robust filtration suit its active sand-sifting lifestyle. Compatible with other Gymnogeophagus and large South American tetras in sufficiently spacious aquaria.

Water: Moderate hardness accepted; pH 6.5–7.8, temperature 18–28 °C seasonally. Tank: 300 L+; fine sand, open areas, robust filtration. Feeding: Sinking pellets, frozen bloodworm, artemia, earthworms occasionally. Breeding: Delayed mouthbrooder; female holds fry 10–14 days; temperature cycling stimulates spawning. Compatibility: Good with robust large tetras and other Gymnogeophagus; avoid small fish.