Sewellia lineolata
Built like a tiny stingray and adapted for whitewater streams. Needs powerheads creating real river-current flow and high dissolved oxygen. Smooth river rock and broad plant leaves are their grazing surfaces. Pair with kuhli loaches and otocinclus for a 'river bottom' community.
Reticulated Hillstream Loach (Sewellia lineolata) reaches 5–7 cm as an adult and needs a minimum tank of 75 L. Native to Central and southern Vietnam, it lives in the bottom (sticks to surfaces) water column with a peaceful temperament. Aim for 20–24 °C, pH 6.5–7.5, and 4–15 dGH hardness. Lifespan is 8–10 years with good care. Keep reticulated hillstream loach in groups of 4+, loose group schoolers need numbers to display natural behaviour. Diet: herbivore (biofilm and algae), Soft green algae, biofilm, Repashy Soilent Green, blanched zucchini, sinking veg wafers. Needs strong oxygenated flow to feed. Plant-safe: Yes. Shrimp-safe: Yes.
Care at a glance
Built like a tiny stingray and adapted for whitewater streams. Needs powerheads creating real river-current flow and high dissolved oxygen. Smooth river rock and broad plant leaves are their grazing surfaces. Pair with kuhli loaches and otocinclus for a 'river bottom' community.
By Mike ElmiraUpdated 3 min read
Part of our complete guide to aquarium fish for the planted tank.
The parameters that decide whether reticulated hillstream loach fits in your tank.
Bottom (sticks to surfaces)
No
Small group of 4+
Balitoridae
Herbivore (biofilm and algae)
Soft green algae, biofilm, Repashy Soilent Green, blanched zucchini, sinking veg wafers. Needs strong oxygenated flow to feed.
8–10 yrs
Medium
Fast oxygen-rich Himalayan foothill streams
Central and southern Vietnam
Tank-mate safety and the species this one is documented to thrive (or fail) alongside.
Cold-tolerant low-flow tolerant fish: White Cloud Mountain Minnows, otocinclus, kuhli loaches (different layer), cherry shrimp. Other hillstream loaches.
Warm-water species (anything needing 26+ °C), aggressive bottom-dwellers, anything that competes for biofilm grazing.
Hard-won lessons from the tank.
Build the tank around flow first, then add the fish. A stream-pump or powerhead aimed at one end with smooth rocks as 'rapids' produces the most natural display. They flatten themselves against the glass when feeding — front-pane biofilm grazing is one of the most charming behaviours in the hobby.
Genus 'Sewellia' honours British marine engineer Robert Sewell. Species 'lineolata' = 'finely lined' for the reticulated pattern.
What can go wrong and how to spot it.
Failure modes, in order of how dramatic the fix is.
Sensitive to copper-based medications and low oxygen. Susceptible to bacterial infections if kept in warm low-flow tanks. Treat them like coldwater fish in a tropical aquarium.
Often sold as 'algae eaters' for community tanks — they're highly specialized flow-and-cold-water specialists and will starve in still warm tanks. They eat biofilm and soft algae, NOT hair algae or BBA.
The practical routine, read top to bottom.
75 L+ with high flow (10–15× tank turnover per hour). Powerhead or stream pump creating directional current along one wall. Smooth rounded river rocks (NOT lava rock — too abrasive). Cool water 20–24 °C. High dissolved oxygen — an air stone or surface-agitating filter return is essential.
3 weeks in a high-flow QT. Watch for white slime film (bacterial infection from poor oxygen).
Where it comes from, how it behaves, and the variants you'll see at retail.
Where it lived before it came home.
Fast-flowing mountain streams of central and southern Vietnam. Cool, highly oxygenated whitewater over smooth rounded river stones. They use modified pectoral and pelvic fins as suction cups to cling to rocks in heavy current.
Biofilm, soft algae, aufwuchs (the entire community of microscopic life on submerged surfaces), micro-invertebrates clinging to rocks.
Wild populations stable but habitat degradation in Vietnam is a concern. Most stock is wild-caught; captive breeding is rare.
How they pair, reproduce, and grow.
Difficult. Mature males have a slightly broader head and visibly thicker pectoral fin rays. Females rounder when carrying eggs. Both sexes share the reticulated 'leopard' pattern.
Rare in home tanks. Reports of success involve high-flow species-only setups with cool water, gravel beds, and patient observation. Eggs are deposited under gravel or in crevices. Fry require strong flow from the moment they hatch.
The named cultivars and the lookalikes worth flagging.
Wild type only. Often confused with Beaufortia kweichowensis (Chinese hillstream loach, plainer pattern) and Gastromyzon spp. (Borneo hillstream loaches, different patterns). All have similar care needs.
Direct answers to the questions search engines and AI assistants surface most often about this species.
Reticulated Hillstream Loach (Sewellia lineolata) needs a minimum tank of 75 L. They live in the bottom (sticks to surfaces) water column and should be kept in groups of 4+, so a longer footprint matters more than depth.
Target 20–24 °C, pH 6.5–7.5, and 4–15 dGH hardness. Acclimate slowly when moving them between water sources.
Shrimp safety: Yes. Plant safety: Yes.
Reticulated Hillstream Loach are herbivore (biofilm and algae). Soft green algae, biofilm, Repashy Soilent Green, blanched zucchini, sinking veg wafers. Needs strong oxygenated flow to feed.
On Fin & Stem's 1–5 difficulty scale this species rates 3/5. Intermediate, stable parameters and a mature tank matter. Breeding difficulty: medium.
Typical lifespan in a well-maintained tank is 8–10 years.
A planted tank is a system. Pair this fish with one entry from each other pillar to plan the whole scape.
