Fire eel

Mastacembelus erythrotaenia

Also known as Fire spiny eel

FreshwaterFish

Fire eel (Mastacembelus erythrotaenia) — Llandor · CC BY-SA 3.0

Care at a glance

Temperature: 75–82°F (24–28°C)
pH: 6.0–7.5
Adult size: 39.4 in (100 cm)
Minimum tank: 132 gal (500 L)
Temperament: Mostly peaceful
Social behavior: Solitary
Swim level: Bottom
Difficulty: Difficult
Breeding: Hard
Rarity: Common
Origin: Southeast Asia (Thailand, Laos, Cambodia, Vietnam, Malaysia, Indonesia)
Family: Mastacembelidae

Overview

Keep one per tank, since they are solitary and will not tolerate their own kind. They are mostly peaceful but big, so only house them with fish too large to be swallowed, and give them a tank of 500 liters or more once they grow. They sit on the bottom, hide by day, and come out to hunt at night, so feed them after lights out with worms, prawns, and other meaty foods. Run the water from 24 to 28 C at a pH of 6 to 7.5, fit a tight gap-free lid because they escape, and dose any medication conservatively since they are scaleless and very sensitive to copper.

In the wild

Fire eels come from slow rivers, floodplains, and still backwaters across Southeast Asia, including Thailand, Laos, Cambodia, Vietnam, Malaysia, and Indonesia. These are warm, soft-bottomed waters where the fish spend the day buried in the substrate. A soft sand bottom is mandatory because they burrow, and sharp gravel scrapes their skin and leads to fatal infections. Give them a tank of at least 500 liters with caves and bogwood for cover, water from 24 to 28 C, and a pH between 6 and 7.5.

Good to know

This is a spiny eel in the family Mastacembelidae, and it is one of the largest, reaching up to 100 cm in the wild though most stay around 50 to 60 cm in a tank. Breeding in home aquariums is hard and rarely done, so almost every fish in the trade is wild caught. They are long-lived, often pushing well past a decade with good care.

Did you know

The fire eel is not a true eel at all. It is a spiny eel, named for the row of short defensive spines running along its back, and its long body and pointed snout just give it that eel-like look. That snout works like a flexible probe, sniffing out worms and small prey buried in the sand at night.