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Hillstream Loach
Sewellia lineolata
Animalia›Chordata›Actinopterygii›Cypriniformes›Gastromyzontidae
📍 Fast streams, Southeast Asia
The Hillstream Loach (Reticulated Hillstream Loach) is a spectacularly patterned torrent fish with a flattened body and enlarged pectoral fins adapted for clinging to rocks in fast-flowing streams. In the aquarium it requires strong water movement, high oxygenation, and cool temperatures mimicking its native Vietnamese mountain streams. It grazes periphyton (algae and biofilm) from hard surfaces and benefits from supplemental feeding with blanched vegetables and spirulina wafers.
Care Guide
Diet
Hillstream loaches are primarily herbivorous grazers that feed on periphyton (algae film and biofilm) naturally present on rocks and tank surfaces. Supplement their grazing with blanched zucchini, spirulina wafers, and high-quality algae-based pellets 2-3 times weekly. Feed small portions that are consumed within a few hours to maintain water quality.
Behavior
These are peaceful, bottom-dwelling fish that spend most of their time clinging to rocks and surfaces using their enlarged pectoral fins, mimicking their natural torrent habitat behavior. Males can be territorial toward conspecifics, so provide ample rock formations and hiding spaces. They are most active during low-light periods and require strong water movement to thrive.
Breeding
Breeding Hillstream loaches in captivity is extremely difficult and rarely successful in home aquariums. They require very specific water conditions including high flow rates, cool temperatures, and precise seasonal triggers that are challenging to replicate. Virtually no documented successful captive breeding exists for this species.
Tank Mates
Similar algae-grazing herbivores with peaceful temperament and comparable water parameter needs
Small, peaceful fish that occupy mid-water zones and prefer similar cool, clean water conditions
Tiny, peaceful danios that thrive in cool water and won't compete for bottom space
Excellent algae eaters that share similar grazing behavior and water parameter requirements
Small, peaceful invertebrates that benefit from high water flow and similar cool temperatures
Common Diseases
Ich (Ichthyophthirius multifiliis)
White spots on body and fins, rapid breathing, lethargy, flashing against surfaces
Raise temperature gradually to 26-27°C (loaches tolerate this temporarily), perform frequent water changes, use ich-specific medication if needed; ensure excellent water quality and strong aeration
Bacterial Fin Rot
Frayed or deteriorating fins, discoloration at fin edges, fin loss
Perform 50% water changes every 2-3 days, maintain pristine water quality with strong filtration and flow, use broad-spectrum antibacterial medication if severe
Gill Parasites
Excessive mucus production, rapid gill movement, loss of appetite, gasping at surface
Increase water flow and aeration, perform frequent partial water changes, use antiparasitic medication designed for loaches; quarantine affected fish
Stress-Related Decline
Loss of appetite, hiding excessively, faded coloration, lethargy
Ensure strong water movement (1200+ GPH turnover), maintain cool temperatures (20-24°C), provide abundant rock formations and low-light areas, minimize tank disturbances
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Tanks keeping this 🐟
Kept by 1 hobbyistCommunity tanks featuring Hillstream Loach.
Quick Facts
- diet
- Herbivore – algae film, periphyton, spirulina wafers, blanched zucchini
- lifespan
- 8–10 years
- max size
- 6 cm (2.4 in)
- tank size
- 20 gallons minimum; long, wide tanks preferred
- temperament
- Peaceful; males territorial toward conspecifics
Water it likes
- ph
- 6.5–7.5
- ammonia
- 0 ppm
- nitrate
- <10 ppm
- hardness
- 5–15 dGH
- temperature
- 68–75°F (20–24°C)