New Caledonia

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 atratus is a stream-dwelling goby from Indonesia, northern New Guinea and islands east to Vanuatu and New Caledonia. Males are blackish, especially on the unpaired fins, and large males appear entirely black between the second dorsal and anal fins. It has been maintained by a few private collectors. Like other Stiphodon it is a specialised algal grazer with an amphidromous life cycle.

Stiphodon rutilaureus is a small rock-climbing goby from fast island streams, from northern Papua New Guinea east to Vanuatu and Fiji. Males are bright orange-red with 9 to 11 vertical bars and a blue upper lip, cheek and opercle. An algal grazer, it needs clean, well-oxygenated, flowing water.

The green swordtail, Xiphophorus hellerii, is a livebearer native to southeastern Mexico, Guatemala, Belize and Honduras. Among the world's most recognisable aquarium fishes, it is ubiquitous in the trade, where selective breeding and hybridisation with X. maculatus and X. variatus have produced a bewildering array of ornamental forms. The name is often misspelled X. helleri.