Zig-zag eel

The zig-zag eel (Mastacembelus armatus), also known as the tire-track eel or white-spotted spiny eel, is a distinctive freshwater fish native to riverine systems across the Indian subcontinent, Sri Lanka, South China, and Southeast Asia including Thailand, Malaysia, Vietnam, Cambodia, and Indonesia. Reaching up to 91 cm (36 in) in length, this elongated, snake-like fish lacks pelvic fins and possesses a continuous dorsal-anal-caudal fin arrangement preceded by numerous spines along the back. Its body is dull brown with darker longitudinal zigzag lines forming a reticulated pattern on the upper two-thirds, providing excellent camouflage in the turbid, slow-moving waters it inhabits.

Despite its intimidating size, the zig-zag eel is generally peaceful toward tankmates too large to be considered prey and can be kept in spacious community aquariums. A minimum of 500 L (130 gal) is required for adult specimens, though juveniles can be raised in smaller quarters. The tank should be well-planted with abundant hiding spots using bogwood, rock caves, and PVC piping, with a sand substrate to allow burrowing. A tight-fitting lid is essential as these eels are accomplished escape artists. Dimmer lighting encourages more active daytime behavior, and water flow should be gentle. They thrive in mildly brackish conditions at 24-28C (75-82F), pH 6.0-7.0, with moderate hardness.

As obligate carnivores, zig-zag eels prefer meaty foods such as prawns, krill, lancefish, earthworms, and frozen bloodworms, though some may accept high-quality sinking pellets once established. They are nocturnal by nature, spending daylight hours hidden among decor and emerging at dusk to hunt. Only one specimen should be kept per tank unless housed in groups of five or more to diffuse conspecific aggression. Breeding has not been documented in home aquariums.