Half-banded Spiny Eel
Macrognathus circumcinctus
Mastacembelidae
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About
The half-banded spiny eel is the smallest spiny eel in regular import and the one most often bought on impulse: a 10 cm brown ribbon with pale oblique bars, sold for a community tank it will quietly empty. Adults reach about 20 cm — FishBase holds a single 28.6 cm record — and a 20 cm eel takes anything under 4-5 cm after dark: neons, ember tetras, dwarf shrimp, fry. The rest of the difficulty is mechanical rather than behavioural. It burrows, so the substrate has to be soft sand a couple of centimetres deep, and every rock and root must stand on the tank base with the sand poured around it, or the eel undermines the pile and is crushed under it. And it escapes. A spiny eel finds the filter cut-out, the heater slot and the gap beside the lid clip, and an escaped spiny eel is a dead spiny eel. Two more things to know before you buy. The accepted name is now Macrognathus circumcinctus, although almost every shop still writes Mastacembelus circumcinctus on the tank. And never read a zig-zag or tire-track label as a spelling of this fish: in English those names belong to Mastacembelus armatus, with M. favus close behind it — a spiny eel that reaches 90 cm, is on Lithuanian shelves too, and needs a tank several times anything quoted on this page.
Care
Sand, never gravel — gravel abrades the skin and the fish cannot bury in it. Place the hardscape directly on the glass and pour the sand in around it, so nothing can collapse when the eel digs beneath it. Every opening in the lid must be blocked rather than merely covered. A 90 cm tank, dim light, gentle flow, and plenty of pipes, caves and shaded planting. 24-27 °C, pH 7.0-7.5, GH 5-15. Feed after lights-out with frozen and live foods; dry food is rarely accepted. One eel per tank unless the tank is large and offers several separate hides: they are peaceful towards fish too big to swallow and territorial towards each other.
Diet
Nocturnal carnivore taking invertebrates and small fishes. Frozen bloodworm, brine shrimp, chopped prawn, mussel and small earthworms, fed after lights-out. Dried foods are rarely accepted. Dwarf shrimp are food, not tankmates.
Tankmate compatibility
Possible with care (367)
Avoid (51)
Computed by the AquaSage engine for a spacious reference tank — always check the full verdict for your exact setup in the calculator.
Telling males from females
There is no reliable way to sex this species by eye. That is the honest answer, not a gap in our data.
All the methods, with diagramsAlso in these lists
Similar species
Same category and the closest water parameters — if this species isn't quite it, start here.
Sold in Lithuania
These Lithuanian shops listed this species in their public catalogue (checked August 8, 2026). Stock moves — ask before you travel.
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Frequently asked questions
- What tank size does a Half-banded Spiny Eel need?
- A Half-banded Spiny Eel needs an aquarium of at least 140 litres (37 US gallons) with a footprint at least 90 cm (35.4 in) long — for this species, swimming length matters as much as raw volume.
- What water parameters does a Half-banded Spiny Eel need?
- Half-banded Spiny Eel does best at 23–28 °C (73.4–82.4 °F), pH 6.5–7.5 and a general hardness of 5–15 °dGH.
- Is the Half-banded Spiny Eel suitable for beginners?
- Half-banded Spiny Eel is a demanding species best attempted with some experience — it needs stable, closely watched conditions to thrive.