The fire eel is not a true eel, but an extremely elongated fish with a distinctive pointed snout and underslung mouth. It is part of a group of fishes called spiny eels that also includes Tire Track and Peacock eels. The group gets its common name from the many small dorsal spines that precede the dorsal fin. The body is laterally compressed, particularly the rear third, where it flattens as it joins the caudal fin and forms an extended tail. The fire eel's base coloring is dark brown/grey, while the belly is generally a lighter shade of the same color. Several bright red lateral stripes and spots mark the body, and vary in intensity depending on the age and condition of the individual. Usually the markings are yellow/amber in juvenile fish, changing to a deep red in larger ones. Often the anal, pectoral, and dorsal fins have a red edging.
The fire eel can grow to a considerable size in the wild with specimens often exceeding 1.2 meters (3.9 ft) in length. However, due to limiting factors in the captive environment they usually reach a maximum of around 55 centimeters (22 in), even in very large aquaria.
Fire eels inhabit river environments with slow to briskly moving water and fine sediment. In the wild they occur across a relatively broad area covering a large part of Southeast Asia including Borneo, India, Malaysia, Myanmar (Burma), Sri Lanka, Sumatra, and Thailand. They are bottom-dwellers that spend large portions of their time buried in the riverbed, often leaving only their snout visible. However, they are voracious predators and when hunting will visit all depths.
Young fish generally adapt very well to a community aquarium. Small specimens up to around 15 centimeters (5.9 in) can be kept in a tank measuring 60 centimeters (24 in) and 75 litres (20 US gal) and are peaceful and nondestructive (although their burrowing nature means that they can uproot plants and move bogwood etc.).
Larger fish require disproportionately larger tanks and their companions must be of commensurate size to deter the fiery predator. This fish is one of the more peaceful types of spiny eel and as a baby will go well with community fish. If kept together with small tetras etc., it will get used to them and leave them alone for a majority of its young hood. It is preferred to be put into a larger aquarium away from the small fish when about 7 or 8 inches. It is very hard to know what it will eat. Knowing what it can eat is not a problem but they sometimes only eat a certain food. The same thing goes for the peacock eel and tire track. This fish will most often eat earthworms or live ghost shrimp. Fire eels do good with peacock eels that are the same size. No other spiny eels.
The fire eel needs a nice smooth substrate. Most commonly used is river stone. Also needed is a lot of plants, logs, caves, or other things to hide in. When getting this fish, do not get anything that will pick at the tail or long delicate nose such as tiger barbs, rope fish, or other nippy fish. A good sized tank for small eels range from 29 to 40 gallons.
Fire eels are intelligent. They quickly learn to recognize their keeper and even readily accept food from the hand. Water should be 25–27 °C (77–81 °F) with a pH of 6–7.5. A little salt is welcomed but not essential.
Fire eels often escape uncovered tanks.
Captive spawning is rare and extremely difficult, even with mature fish over 20 inches (51 cm). Use a large tank with a pH around 7.0, a water hardness from 10–15 dH, and a temperature from 27–29 °C (81–84 °F). They lay 800–1,200 eggs in floating plants (plant spawner). The eggs are clear and measure around 1 millimeter (0.039 in) in size. The young grow quickly, gorging on as much food as is available. Excess food can compromise their health.