Home / Fishes / Spiny eels and swamp eels / Zig-zag eel
No federal permit to keepZig-zag eel
Mastacembelus armatus
Fishes › Spiny eels and swamp eels (Synbranchiformes) › Mastacembelidae (Spiny eels)
The zig-zag eel (Mastacembelus armatus Scopoli, 1777), also known as the Baim, tire-track, tire-track spiny-eel, freshwater spiny eel, or marbled spiny eel, is a species of freshwater ray-finned fish in the family Mastacembelidae.
Care at a glance
Species-specific aquarium care
- Tank: At least 144 in long and 72 in front to back for one adult (adults commonly reach about 35.4 in / 90 cm).
- Water: Freshwater (tolerates brackish).
- Temperature: 72–82°F (range recorded for this species).
- pH: 6.5–7.5.
- Hardness: 0–15 dGH.
- Layout: Lives on or near the bottom: floor space and hiding places matter more than height.
- Diet: Eats a varied diet: mix quality prepared foods with frozen and live foods. 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: “Prefers meaty foods such as prawn, krill, and lancefish.”
- 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: “No reports of breeding in the hobby.”
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
It is native to the riverine systems of the Indian Subcontinent (India, Bangladesh, Pakistan, Nepal), Sri Lanka, South China, Malaysia, Thailand, Vietnam, Cambodia, Indonesia, and other parts of South and Southeast Asia. The species was initially described as Macrognathus armature (Lacepède, 1800).
Quoted from the Wikipedia article “Zig-zag 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 and brackish water, in rivers and streams, lakes, rice paddies. Stays near the bottom. Adults live in highland streams to lowland wetlands. |
| Ground it lives on | Over sand, rock. |
| Water it lives in | Freshwater / brackish water, 72–82 °F (22–28 °C), pH 6.5–7.5, hardness 15 dH. |
| Climate | Tropical climate. |
What this means for care
- Keep water within its wild range, 72–82 °F.
- Use a soft, fine bottom; it lives over fine sediment in the wild.
- Provide rockwork with crevices to hide in.
- It tolerates or needs brackish water; check salinity needs before setup.
Native climate (measured)
Native climate (measured)
| Warm-season highs | about 92°F (up to 102°F in the hottest sampled areas) |
| Cool-season lows | about 56°F (down to 48°F in the coldest sampled areas) |
| Average temperature | 71–81°F across sampled records |
| Relative humidity | 69–77% on average (driest month about 60%) |
| Rainfall | about 1756 mm a year, with strong wet and dry seasons |
Measured at 301 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.
| 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 |
| Biology | Adults live in highland streams to lowland wetlands. Usually found in streams and rivers with sand, pebble, or boulder substrate. They seldom leave the bottom except when disturbed. — 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.
Typical adult weight
Average adult body mass in each database (FishBase gives the maximum recorded weight).
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.
Water hardness
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
- Multi-Omics Reveals the Effects of Spirulina platensis Powder Replacement of Fish Meal on Intestinal Metabolism and Stress in Zig-Zag Eel (Mastacembelus armatus) Sun D et al., Antioxidants (Basel, Switzerland) 2024
- Taxonomic, morphometric and limnological assessment of the commercially important ichthyofauna of Sakhakot Stream, Malakand, Pakistan Attaullah M et al., Brazilian journal of biology = Revista brasleira de biologia 2021
- Transcriptome analysis of the spleen provides insight into the immunoregulation of Mastacembelus armatus under Aeromonas veronii infection Han C et al., Fish & shellfish immunology 2019
- Telomere-to-telomere assembly of a fish Y chromosome reveals the origin of a young sex chromosome pair Xue L et al., Genome biology 2021
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. See all 11 on PubMed → 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.
