Hillstream Loach Species Comparison: Sewellia, Beaufortia and Gastromyzon
Hillstream loaches are among the most fascinating freshwater fish available, with their flattened bodies and sucker-like fins adapted for life in fast-flowing rivers. Choosing between the main genera can be confusing, especially when shops label them generically. This hillstream loach species comparison guide from Gensou Aquascaping at 5 Everton Park, Singapore breaks down the differences between Sewellia, Beaufortia and Gastromyzon so you can pick the right species for your setup.
Sewellia: The Butterfly Hillstream Loach
Sewellia lineolata, commonly called the reticulated hillstream loach or butterfly loach, hails from central Vietnam. It grows to roughly 6-7 cm and displays a beautiful pattern of dark spots and lines on a golden-brown base. Males develop prominent tubercles on the pectoral fins and head as they mature, making sexing straightforward in adults.
Sewellia species are arguably the hardiest of the three genera in aquarium conditions. They tolerate temperatures up to 26 degrees C reasonably well, though 22-24 degrees C is preferred. In Singapore, a clip-on fan or small chiller helps keep temperatures manageable, especially during the hotter months of April to June.
Beaufortia: The Hong Kong Pleco
Beaufortia kweichowensis is often sold as the Hong Kong pleco or Chinese hillstream loach. It reaches around 8 cm and has a flatter, more disc-like profile than Sewellia. The colour pattern features irregular dark blotches over a pale tan background. This species is less commonly bred in captivity, so most stock is wild-caught.
Beaufortia tends to be more territorial than Sewellia, especially among males. Provide multiple flat rocks and smooth pebbles to create separate grazing territories. A 60-litre tank is the minimum for a group of four to five specimens.
Gastromyzon: The Borneo Sucker
Gastromyzon species originate from fast-flowing streams in Borneo, making them a particularly relevant choice for Singapore hobbyists given the geographical proximity. Several species are imported regularly, including G. punctulatus and G. ctenocephalus. They grow to 5-6 cm and display varying patterns of spots and bands depending on the species.
These loaches are the most sensitive to warm water among the three genera. They prefer temperatures of 20-24 degrees C and high dissolved oxygen levels. Running an airstone alongside a powerhead mimics their natural habitat and keeps oxygen saturation high.
Water Parameters Compared
All three genera need clean, well-oxygenated water with moderate to strong flow. Here is how their ideal parameters differ. Sewellia tolerates pH 6.5-7.5 and temperatures up to 26 degrees C. Beaufortia prefers pH 7.0-7.8 and stays comfortable at 22-25 degrees C. Gastromyzon requires pH 6.5-7.5 but demands cooler water at 20-24 degrees C. All three appreciate GH between 4 and 12.
Singapore’s PUB tap water, with its GH of 2-4, is on the soft side. Adding mineral supplements or using a remineralising stone in the filter helps bring hardness into the preferred range.
Diet and Feeding
Hillstream loaches are primarily aufwuchs grazers, feeding on biofilm and microalgae coating rocks and glass. A mature tank with algae-covered surfaces is essential. Supplement with blanched courgette, spirulina wafers and repashy gel food. Avoid relying solely on prepared foods; without natural biofilm, these fish often decline over months.
Position flat river stones under the light to encourage algae growth. Some hobbyists rotate rocks between a sunlit bucket and the tank to maintain a constant supply of fresh biofilm.
Tank Setup Essentials
Smooth river pebbles, flat slate and rounded cobbles form the ideal substrate. Avoid sharp-edged rocks that can damage their delicate ventral surfaces. A river manifold or closed-loop circulation pump creates the laminar flow these fish thrive in. Target a turnover rate of 15-20 times the tank volume per hour for the best results.
Plants that tolerate high flow, such as Anubias tied to rocks and Microsorum pteropus, work well. Avoid fine-leaved stem plants that get battered by the current.
Which Species Suits Your Tank
For beginners or those without a chiller, Sewellia lineolata is the most forgiving choice. Its tolerance of slightly warmer water makes it the most practical hillstream loach species for Singapore’s climate. If you already have a chiller or a cooled fish room, Gastromyzon species reward you with fascinating behaviour and beautiful patterning. Beaufortia falls in between and suits hobbyists who can maintain stable temperatures around 24 degrees C. Whichever genus you choose, prioritise water flow and oxygen over all other considerations.
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