- Scientific name: Macrognathus siamensis
- Synonyms: Mastacembelus siamensis
- Common name: Peacock Eel, Spot-Finned Spiny Eel, Peacock Spiny Eel, Siamese Spiny Eel
- Group: Other fishes
- Habitat: Southeast Asia; India, Thailand, Sri Lanka, Malaysia, Sumatra
- Size: 35 cm
- Biotope: Found at bottom depths in slow-moving or standing waters.
- Social behavior: Peaceful, sometimes shy. Gets along well with own species as long as they are similar in size.
- Diet: Carnivorous; Tubifex, small fish, brine shrimp, mosquito larvae, bloodworms, Cyclops
- Breeding: Very rare in the aquarium.
- Tank: Minimum 100 litres
- Population: 2 fish for 180 litres
- Decoration: For substrate use sand or fine gravel as they like to burrow. Make sure they have plenty of hiding places among roots and rocks. Floating plant cover is good but plants buried in the substrate may get uprooted.
- Temperature: 23-28 °C
- pH: 7-8
- Hardness: 6-25NK°
- Lifespan: 8-12 years
Description: This species has different color and pattern forms depending on its geographical population. The body of the Peacock Eel is elongated with a pointed snout. The back is dark brown while the flanks are light brown. The belly is lighter and there is a fine yellow line extending from the snout to the caudal fin. Five eye-spots can be found on the dorsal and caudal fins. Females tend to be larger with a fuller body shape. They are nocturnal and will bury themselves (except for the head) in the fine sand substrate during the day.
Only a few spiny eels have been bred in the aquarium. Their courtship lasts for several hours, where they chase each other and swim in circles. The eggs are deposited among floating plants. They are sticky so will adhere to the plants and then hatch in 3 to 4 days. The fry becoming free swimming a few more days after that and should be fed nauplii.