fish · Mastacembelidae
Peacock eel
Macrognathus siamensis
Wild range: Mainland Southeast Asia: Mekong basin (Laos, Thailand, Cambodia, Vietnam), Chao Phraya and Maeklong basins, and peninsular and south-east Thailand river systems (FishBase via USFWS ERSS; Fishkeeper; Aquarist Atlas). Introduced and established in south Florida (Everglades National Park and adjacent canals, presumed aquarium release; USGS NAS via USFWS ERSS; first recorded 2002 per Kline et al. 2013); also reported introduced to the Philippines (status unknown). (Asia)
At a glance: Peacock eel care
Compiled reference information. Review the care notes and original sources below.
What temperature is listed for Peacock eel?
The compiled profile lists 23.0–28.0 °C for Peacock eel (Macrognathus siamensis). Check the original sources below for context and differing recommendations.
What tank size is listed for Peacock eel?
The profile lists a minimum tank volume of 55.0 US gallons (208.0 liters). Volume alone does not establish suitability; consider dimensions, group size and other inhabitants alongside the full care notes.
What pH is listed for Peacock eel?
The compiled profile lists a pH of 6.5–7.5. Review the cited care sources alongside the other water parameters in this profile.
Natural habitat
The classic 'peacock eel' of the aquarium trade: a slender Asian spiny eel (Mastacembelidae) with a fleshy, probing snout, a tan to olive-brown body with a pale stripe from snout to tail, and a row of 3–6 black, pale-ringed eye-spots along the base of the soft dorsal fin that gives it its name. Nocturnal and burrowing, it spends the day buried in fine sand with just the snout and eyes showing. Not a true eel (Synbranchiformes, not Anguilliformes).
Where they are found
Catalog primary Macrognathus siamensis (Günther, 1861): valid in ITIS (TSN 650111), accepted in GBIF, and used by FishBase, the Catalog of Fishes (via Aquarist Atlas) and the trade (Fishkeeper/Maidenhead, Atlarium). Authorship is in parentheses because it was described as Rhynchobdella aculeata var. siamensis Günther, 1861 (type locality Petchaburi, Thailand); it was also long placed in Mastacembelus (Mastacembelus siamensis). No newer rename is in use. Trade/common names: Peacock eel (FishBase FAO name), Peacock spiny eel, Spotfin / Spot-finned spiny eel (USGS NAS name), Siamese spiny eel. Identity check: 'peacock eel' maps to M. siamensis in FishBase, USFWS/USGS, Fishkeeper and the care literature; M. aculeatus is the Lesser spiny eel and only occasionally mislabelled as a peacock eel, so this is a labelling caution, not a genuine trade-name split (no deferral). Lookalikes: M. aculeatus (Lesser spiny eel, fine eye-spots and a longer snout), M. circumcinctus (catalog half-banded-spiny-eel, oblique bars), and the much larger fire eel / tyre-track eels (Mastacembelus). FishBase max 30 cm SL; Kottelat (2001) gives 20 cm SL as the usual size. Established non-native population in south Florida.
Aquarium care
Plan at least 208 L / 55 US gal with a long footprint (about 120 cm / 48 in); footprint matters more than height (Atlarium 120 cm and ≥300 L; AquariumLab 55 gal; Fishkeeper). Single adults are sometimes kept in 35–40 gal (AquariumSource; fishstores.org), but an adult reaches 20–30 cm. Keep it at 23–28°C, pH 6.5–7.5 and 5–15 dGH; soft, slightly acidic water suits it best long-term (Fishkeeper; Atlarium; AquariumSource; Aqua-Pedia). A deep bed (5–10 cm) of soft, fine sand is essential; sharp gravel abrades the scaleless skin and leads to infections. Add caves, pipes, bogwood, plant thickets and leaf litter, set decor on the tank base so the eel can't undermine it, keep lighting dim and flow gentle, and fit a completely sealed lid because it is an accomplished escape artist. It needs clean, mature, well-filtered water and is sensitive to copper and many medications. Freshwater only; the 'brackish' claim seen on some sites is not supported.
Feeding
Carnivore. In the wild it feeds at dusk on benthic insect larvae, crustaceans and worms, and occasionally small fish (FishBase via USFWS ERSS). In the aquarium feed live or frozen bloodworm, white mosquito larvae, brine shrimp, daphnia, Mysis and blackworm, plus chopped earthworm or krill for larger fish. Dry foods are rarely accepted at first, though some learn to take sinking pellets. Feed after lights-out or target-feed near its hide so faster tankmates don't take everything (Fishkeeper; Atlarium; AquariumSource; Aquarist Atlas).
Compatibility
Peaceful and shy towards fish too big to swallow, but it will eat neon-sized fish, fry and dwarf shrimp at night. Good tankmates are larger rasboras, gouramis, rainbowfish, medium barbs, peaceful botiid loaches, Geophagus and L-number plecos (Fishkeeper; Atlarium; AquariumSource). Avoid aggressive or greedy bottom dwellers that out-compete it for food. Conspecific tolerance varies: Maidenhead recommends groups of 5+ in a large tank, while AquariumSource reports territoriality and advises one per tank; Atlarium allows singles or small groups. Keep one unless the tank is large with many hides. community_safe true with the no-small-fish caveat; not for nano tanks.
Breeding
Rarely bred in home aquaria. Sexes are hard to tell apart; ripe females look plumper. Reported spawnings follow a simulated rainy season (large cooler, softer water changes and heavy live feeding): the male chases the female until they entwine among floating or fine-leaved plants and scatter adhesive eggs. There is no parental care, so remove the adults. Eggs hatch in about 2–4 days and the tiny larvae need infusoria before baby brine shrimp (Aquarist Atlas; Atlarium; AquariumSource; Fishkeeper).
Sources
Compiled from multiple independent care sheets — not copied from a single site.