Percnopterygionus Stiphodon Goby

Stiphodon percnopterygionus is a jewel of Japan's Ryukyu Island streams, where it inhabits cold, tumbling mountain brooks above waterfalls. The species name references the dramatically pigmented first dorsal fin of males: jet black with a crisp white margin, erect during territorial displays, it is unmistakable. Body colouration in dominant males ranges from blue-green iridescence to charcoal, shifting with mood. Females and subordinate males are pale brown with faint lateral dots. Like all Stiphodon, it is amphidromous and grazes periphyton and algal biofilm from hard substrates. It is intolerant of warm or stagnant water and must be kept with excellent filtration and strong surface agitation. A rare treat for the dedicated hillstream goby specialist.

Water: 20–26 °C, pH 7.0–7.8, GH 4–12, KH 3–8; highly sensitive to low oxygen — maintain vigorous surface movement. Tank: 60 L minimum; cool-running stream biotope with large smooth stones and mature periphyton; avoid warm-water setups. Feeding: Biofilm and algae; supplement with spirulina wafers and Repashy Bottom Scratcher; rarely takes meaty frozen foods. Breeding: Amphidromous; not achievable in captivity under standard conditions. Compatibility: Best with other cool-water hillstream species; avoid tropical community fish.