Fire Eel

Geographic Origin and Biotope: Southeast Asia (Thailand, Cambodia, Borneo, Sumatra). Large slow or moderate flowing rivers. Clay and muddy substrates where they bury themselves during droughts.

Taxonomy and Morphology: Fire Eel (Mastacembelus erythrotaenia). Giant Mastacembelid. Thick and muscular, with the classic prominent fleshy rostrum. Can reach 100 cm (39 inches) in length and a build as thick as a man's forearm.

Social Behavior: Despite its mammoth size, it is renowned for unusual intelligence and sociability. After acclimation, it recognizes the owner, lets itself be petted (hand-feeding) and swims like a ribbon in the water.

Coloration and Sexual Dimorphism: Velvety black/anthracite base color. The entire body is longitudinally striated with bright Fire Red/Orange dashes and stripes, while the fins have a bright red margin. The red intensifies in adults.

Aquarium Setup: Final tank no less than 220-250 cm (86-98 inches / min. 1000 Liters / 260 Gallons). Essential very fine sand (not sharp quartz which eviscerates the eel while digging) and gigantic opaque plastic tubes hidden as a permanent den.

Diet and Feeding: Exclusively carnivorous. Adults: whole fish (sardines), shelled prawns, colossal earthworms, mussels and frogs (frozen). Should be fed sparingly (2-3 times a week) as an adult to avoid intestinal blockage or obesity.

Water Quality: Tolerates wide ranges but produces huge waste (Bioload of a freshwater stingray). Over-filtered tanks (Wet-dry or giant Sumps) are a must. Temperature around 26°C (79°F).

Compatibility and Tankmates: Excellent. Ironically, the "monstrous" Fire Eel is very peaceful. To be kept with Asian Arowanas, Datnioides, and large Barbs (Tinfoil). Will eat any fish that fits in its mouth, but is not quarrelsome or territorial.

Aquarium Reproduction: Never documented. Probably linked to migration to monsoon flooded plains, as for other large Asian eels.

Risks and Diseases: Lethal abrasions. The two biggest killers of the Fire Eel in captivity are the use of coarse gravel (which wears down its mucosa to the point of septicemia) and the absence of a weighted lid, leading it to commit suicide on the house floor.