Palau

The olive flathead gudgeon, Butis amboinensis, is a nocturnal ambush predator from the eastern Indian Ocean to the West Central Pacific. It inhabits brackish estuaries, lagoons and mangroves, entering tidal freshwater rivers to an extent, and often aligns itself with solid surfaces or swims upside-down. It is occasionally exported as bycatch and differs from congeners in lacking enlarged outer teeth and scales on the cheek. It is territorial and should probably be kept singly.

The crazy fish, Butis butis, is a flathead gudgeon of coastal and brackish waters across the Indo-Pacific, from eastern Africa to Fiji. The most commonly traded member of the genus, it has many other names, including crocodile fish, duckbill sleeper and upside-down sleeper. A nocturnal ambush predator, it often swims upside-down, and it is territorial and not sociable with conspecifics, so is best kept singly.

Sicyopus zosterophorus is a stream goby with a patchy but wide range from the Marquesas Islands westwards to Indonesia, Japan and southern China. It is occasionally available in the hobby as the 'flaming arrow goby', 'belted rockclimbing goby' or 'ornate goby', often under the invalid name Sicyopus zosterophorum. It inhabits short coastal streams on tropical islands, typically above waterfalls or cataracts.

Stiphodon pelewensis is a stream-dwelling goby described from Palau and thought to occur through the Mariana Islands and as far as Pohnpei. Its range needs confirmation, since a number of similarly patterned fishes occur across much of Micronesia. It resembles S. weberi, and the two are most easily told apart by the belly, fully scaled in S. pelewensis and unscaled in S. weberi.

Stiphodon percnopterygionus is a small stream-dwelling goby ranging from southern Taiwan through the Ryukyu and Bonin islands to Guam and Palau. Rare in the aquarium trade, it is among the most easily identified in the genus. Males have highly extended fourth and fifth spines in the first dorsal fin, and adults reach only 30-35 mm SL. Like other Stiphodon it is a specialised algal grazer with an amphidromous life cycle.