Fire eel (Mastacembelus erythrotaenia) care guide

Group
Freshwater fish
Other names
Fire spiny eel
Family
Mastacembelidae (spiny eels)
Origin
Lowland South-east Asia – Thailand, Cambodia, Laos, Vietnam, Peninsular Malaysia, Sumatra and Borneo – in slow rivers and flooded plains with muddy bottoms.
Water
freshwater
Maximum size
100 cm
Temperature
24–28°C
pH
6–7
Hardness
Soft to medium, 5–12 dGH
Minimum tank
432 litres
Care level
expert
Temperament
semi_aggressive

Care

The fire eel is the largest member of the spiny eel family and can grow to around 1 m, so it is only for aquarists with a very big tank – at least 120 × 60 cm in base and around 430 litres, with bigger better for an adult. It is not a true eel. Keep just one per tank, as they are often aggressive towards each other. It is nocturnal and likes to bury itself, so use a soft sand substrate and provide caves, large pipes and wood to hide in. Like all spiny eels it escapes through the smallest gap, so a tight, weighted lid is a must. The dorsal spines are harmless. Aim for 24–28 °C, soft to medium water and a pH of about 6–7, with strong filtration and regular water changes, as a fish this size produces a lot of waste. Being scaleless, it can react badly to some medications. Young fish are dark brown to grey with bright red stripes and spots that become stronger with age. Most in the trade are wild-caught; it is also a food fish in its homeland. The IUCN lists it as Least Concern, though it has become scarcer locally because of overfishing. Sources: Seriously Fish (seriouslyfish.com/species/mastacembelus-erythrotaenia/); FishBase (fishbase.se/summary/Mastacembelus-erythrotaenia.html); Wikipedia (en.wikipedia.org/wiki/Fireeel). Checked October 2026.

Diet

Mostly meaty foods: prawn, krill, lancefish, earthworm and similar. In the wild it also takes insect larvae, worms, small fish and some plant matter, though captive fish rarely bother with plants.

Breeding

Only bred accidentally in aquaria, and there are no reliable details. Females in condition look noticeably fuller in the body.

Compatibility and tank mates

Generally peaceful with large fish, but it will eat anything that fits in its mouth, so tankmates must be too big to swallow. Keep only one fire eel per tank. Calm, medium to large fish that are not fin-nippers work best.

Last updated 5 October 2026. Community-edited care guide on Aquatic-Auctions.

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