Peacock eel (Macrognathus siamensis) care guide

Group
Freshwater fish
Other names
Peacock eel, Spotfin spiny eel
Family
Mastacembelidae (spiny eels)
Origin
Mekong, Chao Phraya and Maeklong river systems and southern Thailand – Thailand, Cambodia, Laos and Vietnam – in slow or still water such as swamps, canals and ponds.
Water
freshwater
Maximum size
30 cm
Temperature
23–28°C
pH
6–8
Hardness
3–18 dGH (estimated)
Minimum tank
200 litres
Care level
intermediate
Temperament
peaceful

Care

The peacock spiny eel is a long, scaleless, eel-shaped fish with a row of eye-spots along the base of the rear dorsal fin, which gives it its name. It is not a true eel. Most stay around 20 cm, although they can reach 30 cm. It spends the day buried in soft bottom material with just the head showing, so a soft sand substrate is essential – sharp gravel can damage its skin. Add caves, pipes and wood for extra shelter. Spiny eels are expert escape artists, so the tank needs a tight-fitting lid with every gap covered, including around cables and filter pipes. Around 200 litres with a long footprint is our suggestion as a minimum for an adult. They come from slow, warm tropical lowland waters. Keep the water clean and well filtered, and add it to a mature tank. Being scaleless, it can be sensitive to some medications. Males and females are hard to tell apart from the outside. It is usually sold as wild-caught fish. The IUCN lists it as Least Concern. Released aquarium fish have set up a population in Florida, so never let unwanted fish go in the wild. Sources: FishBase (fishbase.se/summary/Macrognathus-siamensis.html); Wikipedia (en.wikipedia.org/wiki/Macrognathussiamensis). Checked October 2026.

Diet

Feeds at dusk and after dark on insect larvae, small crustaceans, worms and occasionally small fish. In the aquarium offer sinking meaty foods such as bloodworm, blackworm, earthworm pieces and chopped prawn, fed after lights-out so it gets its share.

Breeding

Rarely bred in aquaria. In the wild it spawns in the rainy season when nearby forests flood, and the young grow quickly, reaching about 8 cm within two months of hatching. Sexes are hard to tell apart outside spawning condition.

Compatibility and tank mates

Peaceful with fish too big to swallow, but it will eat very small fish and shrimp at night. Good tankmates are medium-sized, calm species that will not compete too hard for food on the bottom. Avoid nippy or aggressive fish.

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

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