Peacock Eel

Macrognathus siamensis belongs to the Mastacembelidae, the spiny eels — not true eels at all, but elongated perciform fishes with a fleshy, flexible snout used to probe the substrate. The scaleless body is light brown, crossed by a thin pale stripe running from the eye to the tail base, and the rear of the dorsal fin carries three to six pale-ringed ocelli reminiscent of peacock feathers, which is where the common name comes from. The front of the dorsal fin is reduced to a row of short, erect spines sharp enough to pierce skin, so specimens are best moved in a container rather than a net, in which the rays inevitably snag. Reported maximum length is 30 cm, though most aquarium fish stop around 20 to 25 cm. The species inhabits the Mekong, Chao Phraya and Maeklong basins together with the rivers of peninsular Thailand, favouring slow or standing water: backwaters, swamps, canals and ponds over sand, mud or silt. It spends daylight buried with only the head showing, emerging at dusk to sift the top layer of the bottom for insect larvae, crustaceans and worms, and follows seasonal floods into inundated forest. Released by the aquarium trade, it has established itself in the Florida Everglades. A 180-litre tank, longer than it is tall, suits one adult; floor area matters far more than height, and a fine sand bed of at least 5 cm is essential for a scaleless burrower — gravel abrades the skin and invites infection. Roots, leaf litter and shade settle it in, and a tight-fitting lid is not optional, since spiny eels escape through any gap. Peaceful towards anything it cannot swallow, it will swallow anything that fits, so choose sizeable companions. Feed bloodworm, brine shrimp and earthworm, live or frozen; dry pellets are often refused at first. Breeding is rare in captivity and the sexes cannot reliably be told apart.