Home / Fishes / Spiny eels and swamp eels / Fire eel
No federal permit to keepFire eel
Mastacembelus erythrotaenia
Fishes › Spiny eels and swamp eels (Synbranchiformes) › Mastacembelidae (Spiny eels)
The fire eel (Mastacembelus erythrotaenia) is a relatively large species of spiny eel.
Care at a glance
Species-specific aquarium care
- Tank: An adult reaches about 39.4 in (100 cm). That needs a pond or public-aquarium-scale system, far beyond a home aquarium.
- Water: Freshwater.
- Temperature: 75–82°F (range recorded for this species).
- pH: 6–8.
- Hardness: 5–19 dGH.
- Layout: Lives on or near the bottom: floor space and hiding places matter more than height.
- Diet: A predator: feed meaty foods sized to its mouth (frozen fish, shrimp, worms); it will eat tankmates that fit in its mouth. FishBase classes it as a omnivore.
Calculated from this species' own FishBase record: tank size from its typical adult length and swimming zone, water values from its recorded ranges. The group guide below fills in general care.
Care guide
Species care notes
- Tank: a base of at least 47 × 24 in (roughly 114 US gallons); space needed is rated “large tank”.
- Water: soft, acidic water, 75–82 °F, pH 6–7, 5–12 dGH.
- Behaviour: temperament fights its own; a shoaling fish best kept in a group of six or more.
- Difficulty: Moderate (Seriously Fish rating).
Short excerpts from the species profile:
- Setup: “Tank should be well planted with floating plants also used.”
- Diet: “Wild fish are omnivorous and consume a variety of smaller fish, aquatic invertebrates, plant matter and detritus.”
- Tankmates: “Generally peaceful community fish, although care should be taken to ensure tankmates are too large to be considered prey as this species does eat live fish in the wild.”
- Breeding: “Has been occasionally bred in the aquarium but this has been accidental.”
From the Seriously Fish profile for this species, which has the full habitat, maintenance, diet, behaviour and breeding write-up 167
Spiny eels
Applies to most species in this group. Habitat: The listed Asian spiny eels inhabit freshwater rivers, backwaters and floodplains, with fire eels associated particularly with sluggish lowland water. Individual species can differ, so compare with the species numbers above and the linked sources.
Housing & setup
- Use soft sand that permits burrowing; avoid sharp gravel.
- Provide daytime shelters using wood, caves or appropriately sized PVC tubes.
- Fit a close-fitting cover and seal escape gaps.
- Use subdued lighting, floating plants and gentle flow for fire eels.
- The fire-eel profile specifies 48 × 24 × 24 inches, about 114 US gallons, but also reports adults up to 39 inches; plan accommodation around actual adult size and enlarge accordingly.
Climate & lighting
| Water | 75.2–82.4°F |
Diet
- Prawns and krill for large Mastacembelus.
- Lancefish or other suitable meaty foods for large specimens.
- Small live or frozen invertebrates for juveniles and smaller species.
Social life
- Usually house large Mastacembelus singly; small fishes may be eaten. Smaller Macrognathus can be more sociable, but compatibility requires species-specific assessment.
Handling
- For necessary capture use a deep soft net and prepare a deep double bag; minimize abrasion.
Health watch
- Skin trauma from substrate or capture.
- Bacterial skin infections.
- Parasitic infections.
Understanding the animal
About this animal
About this animal
This omnivorous freshwater fish is native to Southeast Asia but is also found in the aquarium trade. Although it has declined locally (especially in parts of Cambodia and Thailand) due to overfishing, it remains common overall.
Quoted from the Wikipedia article “Fire eel” (CC BY-SA 4.0) 174
In the wild
In the wild
From this species’ own FishBase record (habitat, bottom type, water and breeding data), not its family. Good care copies these conditions.1
| Where it lives | Lives in freshwater, in rivers and streams, lakes. Stays near the bottom. A large lowland floodplain species occurring in slow moving rivers and inundated plains. Feeds on benthic insect larvae, worms and some plant material. |
| Water it lives in | Freshwater, 75–82 °F (24–28 °C), pH 6–8, hardness 5–19 dH. |
| Climate | Tropical climate. |
| Wild diet | Hunting macrofauna (predator). |
What this means for care
- Keep water within its wild range, 75–82 °F.
Native climate (measured)
Native climate (measured)
| Warm-season highs | about 90°F (up to 96°F in the hottest sampled areas) |
| Cool-season lows | about 71°F (down to 65°F in the coldest sampled areas) |
| Average temperature | 78–82°F across sampled records |
| Relative humidity | 77–82% on average (driest month about 75%) |
| Rainfall | about 2568 mm a year |
Measured at 35 wild occurrence records sampled against WorldClim 2.1 climate data (1970–2000 averages). Air conditions in the range are ecological context, not enclosure settings: microhabitats such as burrows, leaf litter or basking rocks can be cooler, warmer or more humid.
From the sources
From the sources
Quoted from the matching sections of reputable sources for this exact species. Specialist databases are used first; Wikipedia (community-edited, CC BY-SA 4.0) only fills gaps. Other sources are short credited quotes.
| Overview | The fire eel (Mastacembelus erythrotaenia) is a relatively large species of spiny eel. This omnivorous freshwater fish is native to Southeast Asia but is also found in the aquarium trade. Although it has declined locally (especially in parts of Cambodia and Thailand) due to overfishing, it remains common overall. — Wikipedia (community-edited) |
| Where it lives | Home ranges Population dynamics Growth parameters Max. ages / sizes Length-weight rel. Length-frequencies Mass conversion Recruitment Abundance Life cycle Reproduction Maturity Maturity/Gills rel. — FishBase |
| Behavior | Fire eels occur across a relatively broad area covering a large part of lowland Southeast Asia, including central and southern Thailand, Cambodia, southern Vietnam, Peninsular Malaysia, Borneo (Brunei, Indonesia and Malaysia), and Sumatra (Indonesia). They inhabit slow-moving rivers and flood plains, and are bottom-dwellers that typically are found in places with a muddy bottom. — Wikipedia (community-edited) |
| Appearance and size | The fire eel is not a true eel, but an extremely elongated percomorph fish with a distinctive pointed snout and underslung mouth. It is part of spiny eels family, Mastacembelidae. The group gets its common name from the many small dorsal spines that precede the dorsal fin. — Wikipedia (community-edited) |
| Biology | A large lowland floodplain species occurring in slow moving rivers and inundated plains. Feeds on benthic insect larvae, worms and some plant material. Caught by dry pumping bodies of standing water. — FishBase |
Data and studies
The numbers
The numbers
Each bar is what one source reports. Where several sources weigh in, the dashed gold band marks their average.
Adult length
Maximum recorded length. Measured as total length. Fish in home aquariums often stay smaller than wild records.
Water temperature
Range the species tolerates in nature; aim for the middle.
Minimum tank footprint
Seriously Fish recommends a tank base of at least 47 × 24 in (about 114 US gallons).
Veterinary & husbandry research
Veterinary & husbandry research
- MOLECULAR CHARACTERIZATION AND MORPHOLOGICAL OBSERVATION OF "ZEYLANEMA" NEMATODES IN THE DIGESTIVE TRACT OF FIRE EELS (MASTACEMBELUS ERYTHROTAENIA) RAISED IN AN AQUARIUM IN JAPAN Saito T et al., The Journal of parasitology 2025
Peer-reviewed papers that mention this species alongside captivity, zoos, veterinary care or aquaculture. Some cover several species or mention it only in passing, so check the abstract. 170
Sources for this sheet
- FishBase (Froese & Pauly, eds.), version 24.07 Peer-reviewed researchThe global scientific database on fishes, maintained by a consortium of research institutions; every value is referenced.
- Seriously Fish species profiles Experienced keeper or breederLong-running aquarium reference written and peer-checked by experienced fishkeepers and ichthyologists; each profile covers habitat, tank size, water, diet, behaviour and breeding.
- Mastacembelus erythrotaenia — Seriously Fish Experienced keeper or breederAdded in the 2026 source-checked care-guide review.
- Spiny Freshwater Eels, Family Mastacembelidae — Bob Fenner Experienced keeper or breederAdded in the 2026 source-checked care-guide review.
- Spiny Eel Foods and Nutrition — WetWebMedia Experienced keeper or breederAdded in the 2026 source-checked care-guide review.
- Wikipedia (species article) Community referenceFree encyclopedia; useful overviews with their own citations. Intro text is quoted under CC BY-SA 4.0.
- PubMed (U.S. National Library of Medicine) Peer-reviewed researchIndex of peer-reviewed veterinary, zoo and husbandry research.
- iNaturalist (captive observations) Community referenceCommunity observation platform run by the California Academy of Sciences and National Geographic; observations marked captive show animals living in homes, zoos and aquariums.
