Product Details

Reticulated Hillstream Loach – Sewellia lineolata

The Reticulated Hillstream Loach is a specialist river-style loach with a flattened body, beautiful maze-like patterning and fascinating grazing behaviour. Sewellia lineolata is best suited to mature aquariums with strong flow, high oxygen and established biofilm, making it an excellent choice for aquarists wanting an active, peaceful hillstream fish rather than a standard tropical community bottom dweller.

Key Identification:

Common Name: Reticulated Hillstream Loach
Other Names: Tiger Hillstream Loach, Gold Ring Hillstream Loach, Butterfly Sucker, Hillstream Loach
Scientific Name: Sewellia lineolata
Fish Type: Hillstream Loach / Balitorid-type Loach
Water Type: Freshwater

Natural Range & Habitat:

Sewellia lineolata is native to Vietnam, where it inhabits fast-flowing streams, rapids, riffles and rocky river sections. These habitats are typically shallow, oxygen-rich and exposed to current, with smooth stones, boulders and surfaces coated in algae, aufwuchs and biofilm.

Aquarium care should recreate these river conditions with strong filtration, excellent oxygenation, high surface movement and plenty of smooth rock surfaces for grazing. This species should not be kept in stagnant, overheated or newly set-up aquariums with little natural biofilm.

Appearance & Adult Size:

Reticulated Hillstream Loaches have a flattened, streamlined body adapted for clinging to rocks in current. The body and fins are patterned with dark reticulated lines, rings or maze-like markings over a golden, tan or olive base colour. Their broad pectoral and pelvic fins help them grip surfaces, giving them a butterfly-like shape when viewed from above.

Adults usually reach around 5–6 cm. Males are often slimmer and may show a more angular head and pectoral fin shape, while females tend to be rounder-bodied, especially when well conditioned.

Aquarium Suitability:

This species is best suited to a mature river-style aquarium, hillstream setup or cool-to-moderate tropical community with excellent water movement. Provide smooth stones, rounded cobbles, wood, open grazing surfaces and strong lighting to encourage natural algae and biofilm growth. A powerful filter, additional circulation pump or air-driven flow can be useful.

Reticulated Hillstream Loaches are not suitable for brand-new aquariums, very warm discus-style tanks, low-oxygen setups, dirty substrates or aquariums where algae and biofilm are constantly removed.

Recommended Aquarium Size:

A practical minimum is 90 litres for a small group, with a tank footprint of at least 75 x 30 cm recommended. Larger aquariums of 120 litres or more are preferred for stronger flow, more grazing surfaces and groups of several fish.

Although small, this species needs surface area and water movement more than height. A long, shallow-style aquarium is often better than a tall tank.

Water Conditions:

Temperature: 20–24°C
pH: 6.5–7.8
Hardness: Soft to moderately hard
Additional Notes: High oxygen and clean water are essential. Maintain strong surface agitation, regular water changes and stable conditions. This species can tolerate slightly warmer water if oxygen levels are very high, but long-term care is best in cooler, well-oxygenated conditions. Avoid high nitrate, low flow and sudden temperature swings.

Temperament & Tank Mates:

Aquarium Category: Community Fish

Reticulated Hillstream Loaches are peaceful with other fish, but they can be territorial with one another over favourite grazing stones. This is usually display behaviour rather than serious aggression when the aquarium has enough space and multiple feeding areas.

Suitable tank mates include White Cloud Mountain Minnows, small danios, peaceful rasboras, smaller barbs, Stiphodon gobies, Cory-type catfish in compatible temperatures, bristlenose plecs and other peaceful community fish that enjoy clean, oxygen-rich water.

Avoid large predators, aggressive cichlids, goldfish, very warm-water species, slow long-finned fish in unsuitable flow and boisterous bottom feeders that will outcompete them for food. Keep singly only if space is limited, but groups of 3 or more are better, with 5–6 preferred in larger river-style aquariums.

Feeding:

Reticulated Hillstream Loaches graze on biofilm, soft algae, aufwuchs and tiny invertebrates from hard surfaces. They should not be expected to survive on algae alone. Offer sinking algae wafers, spirulina foods, specialist grazer pellets, soft gel foods, blanched courgette, spinach or other vegetables, and occasional small frozen foods such as daphnia, cyclops, brineshrimp or bloodworm.

Feed after lights-out or place food directly onto rock surfaces if faster tank mates take everything first. A mature aquarium with natural grazing growth is strongly recommended before purchase.

Behaviour in the Aquarium:

This species spends much of its time attached to rocks, glass, wood and décor, grazing with short movements across surfaces. In good conditions it is active during the day and can often be seen displaying, shuffling over stones and defending preferred feeding spots.

Reticulated Hillstream Loaches are excellent climbers and can move up glass and filter outlets, so a secure lid and covered gaps are recommended. Their activity and confidence improve when the aquarium is mature, well oxygenated and not overcrowded.

Care Notes:

Add only to a fully cycled, established aquarium with visible biofilm or soft algae growth. Maintain strong flow, high oxygen and very clean water. Avoid medications containing copper unless confirmed safe for loaches, and never expose them to poor water quality or low oxygen. Do not house in aquariums that are too warm, newly set up or heavily stocked.

Because this is a specialist hillstream species, it is best sold to customers who understand river-style aquarium care and can provide long-term grazing surfaces.

Recommended For:

Intermediate

Availability:

Occasional / Specialist import, with captive-bred availability increasing in some markets

Image Disclaimer:

All images are a visual representation of the fish you will receive, made to be as accurate as possible. Natural variation in size, colour, reticulated pattern, body shape and markings can occur between individual fish.