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Peacock Eel / Spot-finned Spiny Eel
Macrognathus siamensis
The Peacock Eel is a bottom-dwelling Asian fish that buries itself in soft substrates. A large aquarium with a thick, absolutely non-sharp sand bed is mandatory to prevent it from sustaining injuries.
Class:Actinopteri
Order:Synbranchiformes
Family:Mastacembelidae
Genus:Macrognathus
Species:Macrognathus siamensis
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Water Temperature
23 - 28 °C
pH Value
6.5 - 7.5
Water type
Freshwater
Adult size
30 cm
Minimum tank volume
>= 300 L
Minimum group
>= 1
GH
5 - 15 dGH
KH
2 - 7 dKH
TDS
95 - 295 ppm
Conductivity
148 - 461 uS/cm
Species description
Geographical Origin and Habitat: Southeast Asia (Thailand, Mekong Basin, Malaysia). Lives in silty bottoms, rice paddies, swamps and canals with slow waters and a dense tangle of roots and rotting foliage.
Taxonomy and Morphology: Peacock Eel (Macrognathus siamensis). Medium-sized Mastacembelid. Possesses a serpentine anguilloid body ending in a pointed snout prolonged in a rostrum (fleshy proboscis) useful for probing the sand.
Social Behavior: Extremely fossorial and nocturnal. Spends much of the day entirely buried in the sand: only the rostrum (which acts as a snorkel) and the eyes emerge from the substrate, scanning the environment.
Coloration and Sexual Dimorphism: Brown/olive body topped by a golden line along the spine. The dorsal fin, joined to the caudal, presents from 3 to 6 yellow-ringed black ocelli (fake peacock eyes) to disorient predators.
Care, breeding and tankmates
Aquarium Setup: Minimum 120 cm (48 inches) aquarium. MANDATORY REQUIREMENT: thick layer (7-10 cm / 3-4 inches) of fine and absolutely non-sharp sand. Omit heavy furnishings resting on the sand, as its digging activities would cause them to collapse.
Diet and Feeding: Macro-invertebrate carnivore. Ignores flake feeds and struggles to accept dry pellets. Must be fed in the evening (in the dark) with frozen bloodworms, earthworms (chopped) and mysis. Uses the rostrum to flush out buried prey.
Water Quality: Requires clean water but without excessive current. Can tolerate slight additions of salt (very weak brackish water) but thrives in fresh water. The tank lid MUST be totally sealed.
Compatibility and Cohabitation: Peaceful with fish too large to be swallowed (Gourami, Loaches, medium-sized Barbs). Infallible predator of any fry, caridina (shrimp) or small spindle-shaped fish (e.g. Neons) during the night.
Aquarium Breeding: Very rare in captivity without hormonal stimuli. Males chase females until they intertwine among floating vegetation, where they lay adhesive eggs. No parental care.
Risks and Diseases: Skin infections and Escape. If housed in tanks with coarse gravel or sharp quartz, it will flay its belly and proboscis, developing lethal fungal infections. Honorable mention: will escape from any lid hole wider than 1 cm (0.4 inches).
Geographic Origin and Distribution
Southeast Asia (Thailand, Mekong Basin, Malaysia). Lives in silty bottoms, rice paddies, swamps and canals with slow waters and a dense tangle of roots and rotting foliage.
Origin
South and Southeast Asia
Fish profile
- Temperament
- No verified data available
- Diet
- No verified data available
- Life expectancy
- No verified data available
- Adult size
- 30 cm
- Sex ratio
- No verified data available
- Feeding frequency
- No verified data available
- Bioload
- Medium to High
- Flow
- No verified data available
- Jump risk
- No verified data available
- Reproduction
- No verified data available
- Compatibility & tankmates
- With caution
- Tank level
- No verified data available
The catalog's scalar value is 30 cm. The FishBase SPECIES table (v25.04 snapshot) source reports a maximum adult measurement of 30 cm for this species, recorded as standard length (SL). The taxonomic record consulted is Macrognathus siamensis (v25.04); male or unsexed record. These figures are not interchangeable: the first is the profile's editorial reference, whereas the second is a published maximum under a specific measurement convention; differences among sources can reflect sex, population, life stage and measuring method.
The single-adult profile is classified as medium-high bioload. The bioload-v2 rubric deterministically assigns this class from the verified maximum length of 30 cm (≤30 cm band); it is a catalog management category, not a direct measurement of waste output.
They are peaceful towards medium-sized community fish. They will eat tiny fish and small shrimp. Avoid keeping them with aggressive bottom dwellers.
Window to the official scientific data of the species
Data synced on: 06/15/2026
Scientific Parameters & Models
- Trophic level
- 3.3 ± 0.4 se
- Resilience
- Medium (1.4 - 4.4 years)
- Phylogenetic uniqueness (PD50)
- 0.5
- Bayesian Length-Weight
- a = 0.00295, b = 2.94
VulnerabilityLow to moderate vulnerability (27 / 100)
Image gallery
Licensed images linked to the species or, when marked, to the closest representative taxon.
Related species
Recommendations grouped by close relatives, companion choices, and similar care.
