Sewellia lineolata, reticulated hillstream loach, loach

The Sewellia lineolata, commonly known as the reticulated hillstream loach, is an intriguing creature, spending most of its life meticulously scouring the riverbed in search of algae and other organic materials. Native to the swift, shallow rivers and streams of Vietnam, this loach’s biology and behavior are a tribute to the power of adaptation, displaying how organisms can become perfectly suited to their specific environments.

The body of the Sewellia lineolata is striking in its aesthetic appeal. One of its defining features is the intricate pattern of dark, reticulated lines that crisscross its dorsal surface, giving it an almost zebra-like appearance. The overall coloration can range from a pale to a more intense yellow-brown, depending on its environment and diet, creating a beautiful contrast with the dark lines. The body is relatively flat and elongated, similar to a disc, which aids in creating suction, allowing these creatures to stick to flat surfaces against the fast current.

The S. lineolata’s size typically reaches up to around 2.5 inches, or about 6.4 centimeters, with females tending to be larger than males. Males, however, are more brightly colored and have a more complex pattern on their body, especially during the breeding season. They also have modified pectoral fins that display small, comb-like structures known as lamellae that aid in the spawning process.

The Sewellia lineolata, or reticulated hillstream loach, is a gem in the world of aquarists. Its vibrant coloration and fascinating habits make it a unique species to observe, however, replicating the specific conditions of its natural habitat to ensure its successful maintenance can be challenging.

In the wild, S. lineolata is native to the fast-flowing rivers and streams of Vietnam. It is adapted to cool, oxygen-rich water, with a strong current and a rocky substrate, which are vital when setting up an aquarium for these creatures. An aquarium designed to house S. lineolata should incorporate a powerful filtration system to simulate the fast currents of their native environment. Water should be well-aerated and circulated, ensuring high oxygen levels. Ideal water temperatures range from 68 to 75 degrees Fahrenheit, while pH levels should be kept slightly acidic to neutral, between 6.5 and 7.5.

The aquarium should feature a variety of rocks and pebbles, as these serve both as grazing sites and hiding spots for S. lineolata. These loaches are algae grazers in their natural habitat, so an aquarium with well-established algae growth is highly beneficial. In the absence of sufficient algae, their diet can be supplemented with high-quality, vegetable-based sinking pellets, blanched vegetables, and algae wafers.

S. lineolata are primarily bottom-dwelling and their flat, disc-like bodies are designed for clinging onto submerged rocks and surfaces. Therefore, a spacious tank bottom with smooth rocks and pebbles is essential to prevent damage to their delicate undersides. Their preferred habitat also includes plenty of nooks and crevices, so a layout incorporating caves or overhangs created from smooth stones will be well-appreciated.

Sewellia lineolata, reticulated hillstream loach, loach

These loaches are a peaceful, social species and thrive in a group, so it’s recommended to keep several of them together in the same tank. They are known to exhibit social hierarchies and territorial behavior, particularly during breeding season, but they are generally not aggressive towards other species, making them a good candidate for a community tank with other fast-water species.

Breeding in aquarium conditions is rare but not unheard of. Males prepare a flat surface for spawning, usually the underside of a rock, and court females with a dance-like display. After spawning, females lay adhesive eggs which the male fertilizes. It’s important to note that fry are extremely small and require microscopic food like infusoria initially.

Maintaining good water quality is crucial, as S. lineolata are sensitive to poor water conditions and changes in water parameters. Regular water changes, routine tank cleaning, and effective filtration will go a long way in ensuring the well-being of these loaches.

Tank Setup

Sewellia lineolata are schooling fish, so it is important to keep them in groups of at least 5. They also need a tank with plenty of swimming space and a strong current. A good substrate for these fish is sand or gravel, as they like to sift through it for food. You should also add some rocks and plants to the tank for them to hide in.

Water Parameters

Sewellia lineolata prefer soft, acidic water with a temperature of 68-75 degrees Fahrenheit. You can use a water conditioner to soften the water and a pH regulator to bring the pH down to the desired level.


Sewellia lineolata are omnivores and will eat a variety of foods, including flakes, pellets, frozen food, and live food. You should feed them a diet that is high in protein and low in fat.


Sewellia lineolata are active fish that are always on the move. They are also very curious and will explore their tank thoroughly. These fish are peaceful and can be kept with other peaceful fish of similar size.


Sewellia lineolata are generally healthy fish, but they can be susceptible to some diseases, such as Ich and fin rot. You can help to prevent these diseases by keeping the water quality in the tank high and by providing your fish with a healthy diet.


Sewellia lineolata are beautiful and interesting fish that make great additions to any aquarium. They are easy to care for and are compatible with a wide variety of other fish. If you are looking for a peaceful and active fish for your aquarium, Sewellia lineolata is a great choice.

Here are some additional tips for keeping Sewellia lineolata in your aquarium:

  • Provide a strong current in the tank. These fish are used to living in fast-flowing streams, so they need a tank with plenty of movement in the water.
  • Add plenty of plants to the tank. These fish like to hide among plants, so providing them with plenty of hiding places will help them feel secure.
  • Feed them a varied diet. These fish are omnivores, so they need a diet that includes both plant and animal matter.
  • Keep the water quality high. These fish are sensitive to water quality, so it is important to keep the water clean and free of ammonia and nitrites.
  • With proper care, Sewellia lineolata can live for 5-10 years in your aquarium.

By fishexp