Siamese Spiny Eel

Macrognathus siamensis

Photo of aquarium fish Siamese Spiny Eel
Natural range
  • Mekong River Basin
  • Chao Phraya River Basin
  • Mae Klong River Basin
  • Cambodia
  • Laos
  • Thailand
  • Vietnam
Unusual Conservation status: Least concern LC

Family:Spiny Eels (Mastacembelidae)

Other scientific names: Mastacembelus siamensis, Rhynchobdella aculeata

The Siamese spiny eel, scientifically known as Macrognathus siamensis, belongs to the family Mastacembelidae, or spiny eels, and is classified as an eel. It can be found in the wild in Southeast Asia, particularly in the vast basins of the Chao Phraya and Mekong rivers, located in modern-day Thailand. It prefers shallow river areas with soft substrate, often burying itself and leaving only its head exposed.

Required aquarium volume
from 150 L
Size in aquarium
30 cm
Temperature
23 – 28 °C
Temperament
Semi-peaceful
Parameters
Temperature23 – 28 °C
Water pHSlightly acidic (6) – Slightly alkaline (8)
Water dHSoft (6) – Very hard (25)
Water salinityno salt (freshwater)
Size in aquarium30 cm
Lifespan10 years
TemperamentSemi-peaceful
Toward small fisha risk to small fish
Required aquarium volumefrom 150 L
Lightingdimmed
Substratesandy (regular, light)
Water flowmoderate
Swimming levelnear the bottom
FeedingHigh protein
KeepingBoth solitary and in group

Frequently asked questions

The essentials: size, tank volume, water parameters and care

How big does Siamese Spiny Eel get?

An adult reaches 30 cm in length. Plan the tank around the maximum size: the fish quickly outgrows a cramped setup.

What size aquarium does Siamese Spiny Eel need?

The recommended volume is 150 L. A smaller tank speeds up nitrate build-up and raises stress levels.

What water parameters does Siamese Spiny Eel need?

Temperature 23–28 °C, pH 6–8, hardness 6–25 dGH. Stability matters more than exact values: sudden swings are harder on the fish than a small deviation from the ideal.

How long does Siamese Spiny Eel live?

Around 10 years when kept properly. Lifespan depends directly on tank volume, water quality and a varied diet.

Is Siamese Spiny Eel aggressive?

Temperament: semi-peaceful (dangerous to smaller ones). Not a predatory species, but small fish that fit in its mouth will eventually be eaten.

How many Siamese Spiny Eel should be kept together?

Recommended setup: both solitary and in group (flexible). Ignoring this is a common cause of stress and disease.

What does Siamese Spiny Eel eat?

Diet type: high protein (predominantly meat). Feed small portions that are finished within a couple of minutes — overfeeding does more harm than underfeeding.

What is the scientific name of Siamese Spiny Eel?

The scientific name of the species is Macrognathus siamensis, family Spiny Eels (Mastacembelidae). It also appears in the literature as: Mastacembelus siamensis, Rhynchobdella aculeata.

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