Hillstream loach
Sewellia lineolata
intermediate careOverview
The hillstream loach (Sewellia lineolata) is a flattened, tiger-striped little fish that looks and behaves almost like a freshwater ray-cum-limpet, clinging to rocks and glass with a sucker-like body. It’s beautiful and fascinating — but it’s a specialist. Hillstream loaches come from cool, fast, oxygen-saturated mountain streams, and recreating those conditions is the whole job. Give them a proper river-current tank and they thrive; drop them in a typical warm community tank and they slowly starve or suffocate.
Tank & water
A small group needs at least 90 litres (25 gallons), with a long footprint and a smooth rock hardscape.
- High flow and oxygen: this is the key. Strong current, powerheads or a spray bar, and vigorous surface agitation to keep oxygen high. A powerful filter plus extra flow suits them.
- Cool water: hold 18–24 °C. They dislike warmth, which lowers oxygen; keep them at the cool end and avoid heat.
- Mature, algae-grown surfaces: they graze biofilm from smooth rocks and glass, so the tank must be established. Never add them to a new setup.
- A lid: they can climb and jump in strong flow.
Feeding
A dedicated grazer, the hillstream loach rasps biofilm and algae from smooth surfaces all day. In a mature tank much of its diet is natural aufwuchs, supplemented with algae wafers, blanched vegetables (courgette, spinach) and small frozen foods like bloodworm and daphnia. Keep some smooth, well-lit rocks to grow the film it depends on; the fish food range covers the wafers and supplements.
Tankmates
Peaceful and best in a group of three or more, it suits other cool, high-flow-tolerant fish: white cloud mountain minnows, larger danios and other temperate current-lovers. Avoid warm-water tropicals and anything aggressive. It ignores tankmates entirely, spending its time on the rocks.
For gentle grazers that share the workload, see our best algae eaters answer, or the peaceful otocinclus.
Common mistakes to avoid
- Low flow and poor oxygenation
- Keeping them too warm
- Adding them to a new, algae-free tank
- Treating them as a casual community fish
Hillstream loach — frequently asked questions
Why do hillstream loaches need so much flow?
They come from fast, cool, oxygen-rich mountain streams and are built to cling to rocks in strong current. In a still, warm tank they can't get enough oxygen and slowly decline. High flow and good surface agitation aren't optional — they're the core of keeping them.
What do hillstream loaches eat?
Mainly biofilm (aufwuchs) and algae they graze from smooth rocks and glass, supplemented with algae wafers, blanched vegetables and small frozen foods. They need a mature, algae-grown tank — a brand-new sterile setup will starve them.
Are hillstream loaches good for beginners?
They are best for keepers who can commit to a specialist setup: cool, high-flow, well-oxygenated water and a mature tank with plenty of biofilm. In a standard warm, low-flow community tank they usually fail.
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