Matano Lake Medaka

Oryzias matanensis inhabits the ultra-clear, highly oxygenated waters of Lake Matano in South Sulawesi — one of the deepest lakes in the world and a hotspot of endemic biodiversity. Males display attractive black and silver lateral banding, which is more pronounced than in many other Sulawesi Oryzias. The species is considered Vulnerable.

The chemistry of Lake Matano is unique: it is warm, extremely clear, moderately alkaline, and rich in dissolved minerals but with very low organic load. Replicating this in the aquarium is challenging — pristine water quality, low nitrates, and moderate hardness are all important. Peat and tannin-based filtration are counterproductive for this species.

O. matanensis is prized by specialists and contributes to our understanding of the remarkable adaptive radiation of ricefishes in Sulawesi. Breeding has been achieved in captivity and follows standard Oryzias protocols.

Water: 26-30°C, pH 7.5-8.5, moderately hard and clean (GH 10-18, very low nitrates) — Lake Matano conditions. Tank: 40 L species tank; clean alkaline water; no peat or tannins; occasional water changes. Feeding: high-quality micro pellets and live baby brine shrimp; avoid overfeeding. Breeding: standard Oryzias egg scattering; eggs deposited on fine-leaved plants. Compatibility: species-only Sulawesi biotope recommended.