Peacock Spiny Eel
Macrognathus siamensis
The Peacock Spiny Eel (Macrognathus siamensis) is an aggressive fish that's best left to experienced keepers. Give it a tank of at least 265 litres (70 US gallons), water held at 75-82°F, and a pH of 6.5-8.5.
Captive lifespan reflects typical experience in a home aquarium, not maximum recorded age; genetics, sourcing, and care vary.
Natural distribution
Africa / South America (varies)
- Africa
- South America
Regional colours match the stocking calculator's origin map.
Peacock Spiny Eel Tank Setup
Give them at least 265 litres (70 US gallons). Cichlids are territorial and produce plenty of waste, so strong filtration and some rocks or wood to break up sight lines both help. Aim for 75-82°F and a pH around 6.5-8.5. They grow to around 30 cm, so plan the tank size and filtration for a full-grown adult rather than the small juvenile you see in the shop.
What Do Peacock Spiny Eels Eat?
They're not fussy eaters - feed a varied diet, rotating good-quality dry, frozen, and gel foods rather than the same thing every day, and match the food size to their mouths.
Peacock Spiny Eel Tank Mates
May nip fins; avoid with long-finned or slow tankmates. Predatory; may eat small fish or inverts. Requires a large tank and good filtration. The Peacock Spiny Eel is aggressive, which is the first thing to weigh up when you choose tank mates. It's a known fin-nipper, so avoid bettas, guppies, and other slow, long-finned fish. It's predatory, so anything small enough to fit in its mouth will be treated as food rather than a companion. Before you buy, run your full stocking list through our stocking calculator. It weighs temperament, adult size, and water needs together, which a single species page can't do on its own.
Are Peacock Spiny Eels Good for Beginners?
Not a sensible first purchase. Get the tank cycled, keep easier fish stable for a year, then revisit if you still want the extra work this species demands.
Peacock Spiny Eel - frequently asked questions
What size tank do Peacock Spiny Eels need?
Peacock Spiny Eels need a tank of at least 265 litres (70 US gallons). A bigger tank is always easier to keep stable, and gives them more room to settle in and behave naturally.
What water parameters do Peacock Spiny Eels need?
Keep them at 75-82°F with a pH of 6.5-8.5, steady rather than chased to an exact figure. In a cycled tank, ammonia and nitrite should both read 0 ppm, with nitrate kept low through regular water changes.
What do Peacock Spiny Eels eat?
Peacock Spiny Eels are omnivores and aren't fussy eaters. Feed a varied mix of good-quality dry, frozen, and gel foods, and match the food size to their mouths. Feed small amounts once or twice a day, and remove anything they don't eat.
Are Peacock Spiny Eels good for beginners?
Peacock Spiny Eels are not a beginner species. They need precise conditions and consistent maintenance, so build experience with hardier fish before keeping them.
Common mistakes with Peacock Spiny Eels
- Underestimating tank size - the minimum footprint is 265 litres (70 US gallons); impulse buying into a smaller tank leads to stress and shortened lifespan.
- Mixing with long-finned fish - Peacock Spiny Eels will nip at bettas, angelfish, and other fish with flowing fins, causing stress and infection risk.
Building a community? Run the full list through the stocking calculator before you add anything else.
Great tank mates
Chosen from temperament, overlapping temperature/pH bands, plausible minimum tank footprints, and size versus yours in App-aquatic data. Hobby nuance always wins - verify stocking and temperament before purchasing.
Fish to avoid mixing with Peacock Spiny Eels
These well-known species are commonly sold alongside this fish but are not recommended tank mates - verify before purchasing.
- Pea PufferPredator - Pea Puffer will eat or injure smaller tank mates
- Betta (Male)Predator - Betta (Male) will eat or injure smaller tank mates
- Cardinal TetraSize risk - Peacock Spiny Eels will likely eat Cardinal Tetra at adult size
