黑鳍枝牙鰕虎

Overview

The greatly extended fourth and fifth spines of the male's first dorsal fin help identify Stiphodon percnopterygionus. Males may be blue or yellow-orange; these colors are not a simple male-versus-female distinction. Established biofilm and stable oxygenated water are central to keeping this small goby.

Distribution & habitat

Its range arcs from southern Taiwan through Japanese island groups, including the Ryukyus and Bonins, toward Guam and Palau. Typical habitats have gentle gradients and relatively broad slow-to-moderate runs interrupted by pools or small cascades. Clear water and light sustain rich films over the rocky bed.

Aquarium setup

Arrange rounded stones over sand or gravel, placing heavy rocks securely on the base before adding substrate. Digging must not undermine them. Provide cover, visual barriers, and enough grazing area for multiple males. Strong illumination supports algae; seasoned wood and hardy plants are optional, while heavily staining new wood is less suitable.

Maintain filtration, aeration, and circulation. Suggested turnover is roughly 10–15 tank volumes hourly, or 5–10 with good oxygenation. Change about 30–50% of the water each week without removing all useful biofilm. A tight cover prevents climbing escapes. A natural cool season does not justify abrupt aquarium temperature changes.

Diet & feeding

Benthic algae and their associated microorganisms form the food base. Accepted sinking foods or small animal items are occasional supplements. Algae-covered stones grown separately under bright light can replenish depleted grazing surfaces. Tough black brush algae is not a dependable food source. Thin fish particularly need uninterrupted access to suitable food without strong competitors.

Behaviour & compatibility

Peaceful fishes of similar size using higher levels can be suitable companions. Avoid large species, forceful feeders, and most territorial bottom-dwelling cichlids. Males compete for space, so provide room and cover. A suggested small group contains one male and at least two females.

Sexual dimorphism

Young males are usually blue. Many later become yellow or orange, some subsequently return to blue, and others never change. Both color phases can breed. The male's first dorsal is normally black but may look red under stress. Females are relatively plain with two dark, irregular-edged lateral stripes.

Breeding

Adults reproduce in freshwater, while larvae develop at sea before returning upstream. Research on this species found transparent pelagic larvae becoming pigmented after settlement. The pelagic period lasted 78–146 days and increased at lower temperatures. Gonadal activity declined during the cool season, with breeding thought to pause then; peak activity was from June through November.

Under-rock spawning and male egg care are characteristic of the genus. Completing the marine larval phase remains the central aquarium challenge, rather than simply obtaining eggs.

Notes

The elongated first dorsal, dark fin coloration, and small adult size are useful together for identification. Reasons for male color changes remain unresolved, so they should not be treated as a simple indicator of health or maturity.