Half-banded Spiny Eel
Macrognathus circumcinctus
The Half-banded Spiny Eel (Macrognathus circumcinctus) is an aggressive fish that's best left to experienced keepers. Give it a tank of at least 215 litres (57 US gallons), water held at 75-81°F, and a pH of 6.5-8.
Captive lifespan reflects typical experience in a home aquarium, not maximum recorded age; genetics, sourcing, and care vary.
Natural distribution
Various
We don't shade a region on this simplified map - your text may be Europe-only, worldwide, listed as "Various," captive-only, or outside the five areas used in the stocking calculator. That tool still scores whether your fish come from similar parts of the world.
Regional colours match the stocking calculator's origin map.
Half-banded Spiny Eel Tank Setup
Treat 215 litres (57 US gallons) as a starting point - big predators need length, strong filtration, and a secure lid. Hold the water at 75-81°F and pH 6.5-8, and assume anything small enough to swallow will eventually be eaten. They reach about 20 cm as adults, so don't be misled by the small juveniles sold in stores.
What Do Half-banded Spiny Eels Eat?
They're meat-eaters, so feed good-quality frozen or gel foods rather than relying on generic flake. Go easy on portions - leftover protein fouls the water faster than plant foods do.
Half-banded Spiny Eel Tank Mates
Predatory; may eat small fish or inverts. Requires a large tank and good filtration. The Half-banded Spiny Eel is aggressive, which is the first thing to weigh up when you choose tank mates. 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 Half-banded 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.
Half-banded Spiny Eel - frequently asked questions
What size tank do Half-banded Spiny Eels need?
Half-banded Spiny Eels need a tank of at least 215 litres (57 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 Half-banded Spiny Eels need?
Keep them at 75-81°F with a pH of 6.5-8, 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 Half-banded Spiny Eels eat?
Half-banded Spiny Eels are meat-eaters. Feed good-quality frozen or gel foods rather than relying on generic flake, and don't overfeed. Feed small amounts once or twice a day, and remove anything they don't eat.
Are Half-banded Spiny Eels good for beginners?
Half-banded 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 Half-banded Spiny Eels
- Underestimating tank size - the minimum footprint is 215 litres (57 US gallons); impulse buying into a smaller tank leads to stress and shortened lifespan.
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 Half-banded Spiny Eels
These well-known species are commonly sold alongside this fish but are not recommended tank mates - verify before purchasing.
- OscarPredator - Oscar will eat or injure smaller tank mates
- Serpae TetraFin nipper - will shred the fins of peaceful fish
- Zebra DanioFin nipper - will shred the fins of peaceful fish
