Sewellia lineolata

The Reticulated Hillstream Loach, scientifically known as Sewellia lineolata, is a highly specialized fish adapted to life in torrential, oxygen-rich waters. Its native habitat consists of fast-flowing rivers and streams in Asia, where it uses its uniquely flattened body and modified fins to create suction, allowing it to adhere firmly to rocks and driftwood amidst powerful currents. Replicating this environment is the key to successfully keeping them. An aquarium for these loaches must have exceptionally high water flow, typically created with strong filters and additional powerheads or circulation pumps. The water should also be highly oxygenated, a condition directly linked to the water movement.

These fish are social and exhibit complex behaviors when kept in appropriate groups. A school allows them to feel secure and reduces stress, leading to more natural activity. While designated as territorial, their interactions are rarely aggressive. Instead, they engage in ritualized chasing and 'wrestling' to establish a pecking order, particularly over prime grazing locations covered in biofilm. They are constantly active during the day, darting between rocks and skimming over the substrate. As omnivores, their primary diet in the wild consists of the biofilm and algae they scrape from surfaces. In captivity, this should be supplemented with a variety of foods, including algae wafers, sinking pellets, and protein-rich frozen foods to ensure a balanced diet. Due to their active nature and medium metabolism, they require daily feedings. Water quality must be kept pristine, as fish from such dynamic natural environments are often sensitive to dissolved organic waste. Their low waste production is beneficial, but consistent maintenance is still essential.