Hillstream Loach (Sewellia lineolata): Care Guide


Common Name(s)Hillstream Loach, Reticulated Hillstream Loach
Scientific NameSewellia lineolata
OriginLaos and Vietnam
Temperature68-75°F (20-24°C)
Size2-3 inches (5.1-7.6 cm)
Minimum Tank Size55 gallons (208 L)
Food & DietOmnivorous bottom feeder with a preferance towards a plant based diet.
Lifespan8 to 10 years
Water pH6.5 to 7.5
Tank MatesSmall, peaceful freshwater fish.
BreedingBreeding pair will spawn in a nest built in the substrate by the male.
DiseaseMay be susceptible to Ich.
Hillstream Loach
Hillstream Loach (Sewellia lineolata)

Hillstream Loach Facts

Reticulated Hillstream Loaches originate from Vietnam and can be found in fast-flowing waters located within Laos; Quang Ngai; Thua Thien-Hue; Binh Dinh and Quang Nam. They have hydrodynamic characteristics, such as a smooth body (their scales are tiny), depressed undersides, wing-like pectoral and pelvic fins and rays. Their underside and fins work as powerful ventral discs, which give them the ability to cling onto stones and smooth surfaces while facing violent currents. Hillstream Loaches can also crawl and climb upwards out water to feed on insect larvae. Their marking (reticulated) resemble that of a snake, though their body is reminiscent of a manta ray, especially when they swim. The Hillstream Loach is considered one of the most aesthetic and entertaining of its species, captivating both aquarists and anyone who happens to discover this fish. 

Hillstream Loach Care

Hillstream Loaches are only for advanced fish keepers because of their tank set up, temperature and water purity requirements. Their lack of scales on their smooth bodies means that they are intolerant of water spikes, illness and chemicals. Hillstream Loaches demand commitment from aquarists, as they are able to live for more than 8 years; therefore, only people who are dedicated to their care and unafraid of doing thorough research should purchase this species.

Hillstream Loach Temperature

Hillstream Loaches need cool waters, thus temperatures must be between 68° to 75° Fahrenheit (20° to 24° Celsius). As a general rule, this species can temporarily survive in temperatures higher than 75° F (24° C), on the condition that its water is highly aerated; however, long-term exposure to high temperature will result in the Hillstream Loach’s fatality.

Hillstream Loach Water Parameters

Hillstream Loaches need clean, well-oxygenated water with excellent flow to mimic the fast currents this species inhabits. The pH range needs to be in the range 6.5 to 7.5 (moderately acidic), with medium water hardness of 18 to 179 ppm. Testing kits are useful when needing to measure the amount of ammonia, nitrite in the, water which must always remain at zero, while nitrates should never surpass 20ppm.

Hillstream Loach Size

Hillstream Loaches are typically small, with adults reaching a mere 2 to 3 inches (5.1 to 7.6 cm), making it easy for them to scavenge food in the smallest of nooks and crannies within their rocky riverbed terrain. Despite their size, they are not shy creatures and hobbyists can spot them sucking on rock decor or climbing the glass surface of their aquarium. Shops will normally stock Hillstream Loaches that are an average size of 1 to 2 inches (2.5 to 5.1 cm), but they will grow with time.

Hillstream Loach Tank Size

Hillstream Loaches require a tank of minimum 55 gallons (208 L) per 3 to 4 Loaches. It is important to pick a tank that is long and rectangular in shape, due to the Hillstream Loach’s preference for living mostly at the bottom. This surface area will be fitting for intense water circulation and creating a high concentration of oxygen. The tank must possess a dimension of at least 52 L x 24 W x 16 H inches (132 L x 61 W x 41 H cm). If fish keepers are attempting to breed this species, then the pair may be kept in tanks smaller than 55 gallons (208 L).

Reticulated Hillstream Loach

Hillstream Loach Food & Diet

Omnivorous by nature, wild Hillstream Loaches will typically feed on benthic algae, biofilm, aufwuchs, and may occasionally eat nearby insect larvae. It may take some time for the fish to become acclimatised to its aquarium, especially as their shipping conditions can be unpleasant, but Hillstream Loaches will soon be comfortable with accepting new foods. If needed, aquarists should make it clear to sellers that this species of fish must be packaged in separate, tightly sealed bags due to their high oxygen demands.

It is important to note that despite being omnivores, their diet should not consist of too much animal protein, as this will impact their health negatively, even leading to death. Therefore meat should be provided every now and again, in the form of Micro-crustaceans; Daphnia; Gel Fish Food; Frozen/Thawed Bloodworms; Insect Larvae; Brine Shrimp; Cyclops, Mysis Shrimp, Tubifex; Lobster Eggs; and various Marine Plankton.

Hillstream Loaches thrive in mature aquariums that have plenty of rock works covered in algae, which they will happily snack on throughout the day. Ideal vegetable options include: blanched lettuce leaves, zucchini, kale leaves, spinach; and raw cucumber slices. When it comes to algae, this species prefers soft, green algae and aquarists should avoid tough, rubbery-like algae such as Audouinella, Filamentous algae, Compsopogon caeruleus, and Rhodochorton, because Hillstream Loaches will not eat these. Spirulina, aufwuch and algae wafers are excellent food options; however, flakes/pellets/tablets may not produce interest as they are difficult for Hillstream Loaches to consume due to the anatomy of their mouth. They possess no teeth, instead their thick lips have multiple, tiny ridges that scrape biofilm off of rocks and gravel. Their inferior mouth (more of a sucker) is located on the bottom-side of their body, which is unable to catch sinking pellets as they drop.

Because algae is a staple food source for Hillstream Loaches, it is vital that they are able to access enough to keep them from starving. Keepers must be wary of community tanks with too many herbivorous fish as it can limit their Hillstream Loach’s nourishment. Hillstream Loaches will also compete with each other for territory and food, thus the quantity of food must adjusted so all the fish receive plenty to eat. An additional tank with specific conditions for colonising algae on rock formations is ideal, as the fish can be transferred between tanks.

Hillstream Loach Lifespan

Hillstream Loaches will live between 8 to 10 years, provided that they receive a proper diet, water with high purity/aeration, and low temperature. 

Hillstream Loach Tank Setup

Aquarists will need to prepare a river manifold tank with non-perforated tubes as this will allow for highly-aerated, extreme flowing, clear water, which mimics the Hillstream Loach’s powerful, shallow native streams. Combined with enough light, this will also allow for the speedy growth of biofilm.

Fish keepers should add some live plants, as this will help keep nitrate levels low and the dense vegetation will provide ample hiding areas and scavenging sites. Ideal plant options include: Dwarf Aquarium Lily; Anubias Barteri; Hornwort; Water Wisteria; Crinum; Cryptocoryne Beckettii; Java Moss; Aponogeton Ulvaceus Bulb; Microsorum Pteropu; and many more. Keepers can even indulge in Aquascaping, provided that they understand the Hillstream Loach’s serious tank demands. Additional decor that hobbyists can purchase or self-assembled include caves; aged driftwood; clay ornaments; and rock crevices that are smooth and hollow enough to allow the Hillstream Loaches to take cover.

Water changes must take place once a week to maintain the pristine environment essential for this species. Bright artificial LED lights supply the finest milieu required for the colonisation of algae, especially if they are at minimum 40 watt tubes. However, Hillstream Loaches also appreciate plenty of dark spots where they can hide, so a careful balance between brightness and subdued lighting must be created in the tank.

A bottom-dwelling species, substrate such as soft sand or fine gravel is preferred due to their smooth bodies which can easily be scratched by rough objects if they are in the midst of surfing from one place to another. Smooth rocks make a great addition, whether they are elevated or small pebbles. Hillstream Loaches are capable of scaling the glass wall of their tank, so a tight lid must be fitted to prevent them from falling out and suffocating.

The tank must be set up with an over-sized power filter or external tank filter, with extra power-heads/airstones to create a powerful current that will allow Hillstream Loaches to thrive. It is advised that the filter be able to pump 20 times the volume of the tank per hour. If any Hillstream Loaches are missing from the tank, they might have wriggled inside filter or had their fins stuck by accident. A sponge, mesh intake, or a media bag can prevent this from happening.

Are Hillstream Loach Nocturnal?

Hillstream Loaches (Sewellia lineolata) are one of the only species of loaches that are strictly diurnal and remain active during the daytime. When they retire to sleep, the loaches will hide away in dense foliage or cave-like arrangements.

Hillstream Loach Care Guide – ​Amazing Oddball Algae Eater

Hillstream Loach Tank Mates

It is important that fish keepers provide a large enough tank for any species of loach, as they will harass each other for space and food, causing causing high-levels of stress. Bottom-dwelling fish housed with Hillstream Loaches must have enough surface area, food and hiding spots. Loaches may eat fry of other fish species (even their own), so a breeding box for safe spawning is recommended. This species will not bother any fish that looks physically diverse to them.

Compatible Tank Mates

Small, peaceful freshwater, bottom-dwelling fish are best, for example: Rasbora, Stiphodon; Tetras; Sicyopterus; Dwarf Shrimp; Snails, Tanichthys; Danio; Akysis; Devario; Rhinogobius; Glyptothorax; Hara; other Loaches from Gastromyzontidae, Nemacheilidae, and Balitoridae families.

Incompatible Tank Mates

Any larger, aggressive/territory-hungry species that will see Hillstream Loaches as prey is not recommended, such as aggressive barbs (e.g. Tiger Barb) and Cichlids (e.g. African, Oscars). Less dominant, similarly-shaped Loaches will be bullied to starvation, such as: Homaloptera; Annamia; Hypergastromyzon; Liniparhomaloptera; Gastromyzon; Vanmanenia; and Formosania.

Are Hillstream Loach Aggressive?

Hillstream Loaches are one of the most peaceful species of fish, suitable for community tanks and are not exclusively aggressive. Males can display dominant and territorial behaviour when it come to guarding their own personal spots. Hillstream Loach males engaged in fights will often push against each other belly-to-belly in a show of dominance, though this is intended as more of a display rather than intent to harm the other.

How many Hillstream Loach should be kept together?

Hillstream Loaches are very social and it is advantageous that they are kept in groups of at least 6, though the more loaches per tank the better. A Hillstream Loach on its own will become lonely and anxious. A pair of loaches is not recommended due to the fact that one of them may bully the other and outcompete them for food/territory, which is why they are better off in schools.

Hillstream Loach and Goldfish

Goldfish are a friendly species that will co-exist happily with Hillstream Loach. Both have similar water parameters and fish keepers will need to provide a large enough space with plenty of food, hiding spot, and well-oxygenated water for them to thrive. Goldfish will need an area where the water flow is a little less intense so that they can rest.

Hillstream Loach and Shrimp

Dwarf freshwater shrimp (such as Neocaridina davidi) make excellent tank mates for Hillstream Loaches as they are a peaceful species and hail from the same continent, making their water parameters compatible. Because Hillstream Loaches need fast water flow in their tank, the shrimp will need places where they can get out of the strong current, such as caves, clay pots, and rocks.

Hillstream Loach and Guppies

Guppies prefer slow-moving currents and are usually found in ponds, lakes/rivers, in contrast to Hillstream Loaches that thrive in extreme-flowing water. Therefore these two species are incompatible, as they have diverse tank set up demands.

Hillstream Loach and Angelfish

In the wild Angelfish live in deep, slow-moving rivers and lakes, thus depositing them in a tank with a fast-moving current will stress this fish out, hindering their feeding and breeding. Angelfish are also very territorial and will bite the Loaches, who will perish quickly from the stress. Thus, Hillstream Loaches and Angelfish are incompatible tank mates and should not be housed together.

Hillstream Loach and Axolotl

Axolotl’s present a potential health threat for other fish, including Hillstream Loaches, because of their tendency to nip their tank mates, which can cause severe damage. Axolotls also find fast water currents very stressful, therefore they are not compatible with Hillstream Loaches.

Hillstream Loach and Discus

Discus inhabit slow-moving waters and are not comfortable in fast currents, hence they are not compatible with Hillstream Loaches.

Hillstream Loach and Otocinclus

 The Otocinclus appreciates moderate to slow-flowing streams and compact rivers, making it an unideal tank mate for Hillstream Loaches, who need fast-flowing water in their tank.

Hillstream Loach and Betta fish

Bettas have difficulty swimming in intense water current and if the filter is too powerful it can even suck the Betta into the intake tube, drowning the fish. Bettas are also incredibly aggressive and will fight each other to death, with even their females getting into violent skirmishes. Thus, Hillstream Loaches and Betta are not compatible tank mates.

Hillstream Loach and Corydoras

Corydoras generally live in South American, slow-moving, marshes, streams, rivers, and ponds. Despite this, the Corydoras adore fast-flowing water and are often found playing and mating in them. Hillstream Loach and Corydoras are compatible, provided that fish keepers supply their tank with plenty of shelves and plants to rest from the strong currents.

Hillstream Loach Breeding

While Hillstream Loaches are difficult to breed, it is not impossible to do in captivity if the correct environment is supplied. This species remains the easiest to breed out of the Loach species.

Hillstream Loaches are sexually dimorphic and fish keepers can tell them apart when they reach adulthood, as juveniles are incredibly hard to sex. Therefore, if fish keepers are intending to breed their Hillstream Loaches, they might need to buy a large group of juveniles. Sexually mature females possess a stouter silhouette and a wider head, which extends to their pectoral finds, although they are smaller in length compared to their male counterparts. Males have a less-rounded body, a prominent square-shaped snout and their pectoral fins grow out from their sides, with subtle ridges forming at an angle.

A separate, well-established aquarium solely for breeding Loaches is required to prevent predatory fish from consuming the eggs and fry. A breeder box can be useful to have if hobbyists are concerned about the survival rates of their fry. Many aquarists have had positive outcomes when they provided plenty of detritus; infusoria; algae; and mulm, which the fry were able to hide in and graze on before expanding their diet to also consume vinegar eels; brine shrimp; plankton; micro-worms; powdered fry food, etc. It is crucial that keepers cover their canister filters, power filters and pumps with pre-filter sponges to prevent the fry from getting sucked into them.

Mating can be provoked by increasing the temperature to maximum 78° Fahrenheit (26° Celsius) and then performing a cool water change. However, some aquarists have found that a temperature spike is not entirely necessary and that simply feeding the Hillstream Loaches well is enough to encourage breeding. Males begin courtship by undulating themselves while chasing after the females. When a female loach is favorable to this treatment they will stay close to him, while the male builds a nest in the substrate for their eggs.

When ready to mate, the male will start shoving at her dorsal area with his snout, endeavoring to push her from any surface she might be attached to. The two wind their pectoral fins together before the female releases her eggs into the nest, where the male then releases milt to fertilize them. Some fish keepers state that incubation lasts a couple of weeks and if fries can be seen in the tank, it is time to start feeding them.

Adult Hillstream Loaches can be left with the fry if they are minimum 5mm, but it is good practice to add plenty of hiding spots, such as smooth rock piles, a large area of rounded river gravel and dark-coloured spawning mops (non-dye acrylic yarn or wool)  for them to take cover in. The fry will be less pigmented compared to the adults, slimmer, and possess tiny, spikes protruding from its snout, which becomes less noticeable when they reach maturity.

Hillstream Loach Disease

Although Hillstream Loaches eat algae, fish keepers should keep an eye out for a bloom of blue-green algae, as the presence of too much cyanobacteria is a sign of poor water conditions and is toxic to aquatic life. Water contamination can occur because of overfeeding, overexposure to light, too many fish, too few water changes and aquarium maintenance.

Hillstream Loaches are very active, social creatures that have a healthy appetite for foraging. Common signs of illness include: lack of appetite, inactivity, isolating themselves from their group, repeatedly rubbing their body against rocks or gravel (“flashing”), areas of sores or ulcers; flushed skin; and bloody fins.

Ichthyophthirius multifiliis, Ich, or White Spot Disease is a common external parasite that can be seen across a fish’s body in the form of white spots. Newly-bought fish should be placed in a separate tank before being added to the community tank once the infection passes. To combat this aquatic parasite, aquarists must treat the tank with a 50% water change and vacuum the substrate and plants. All the water-changing supplies have to be rigorously cleaned and dried before using it. Carbon in filters must be discarded, as it may store Ich cells. The water temperature must gradually be increased to 86° Fahrenheit (30° Celsius) over 24 hours. A loach-safe OTC Ich medication must be added to the water, but salt should never be used (even if the instructions insist) because this stresses Hillstream Loaches even more. Water levels need to be decreased to increase oxygen levels, which will aid the Loaches in their recovery. After 2 days, the tank should be dosed again and a 50% water change has to be done, before yet another dose is administered to the water again. This cycle of water changes followed by the medication must be repeated at least 4 times, even if the white spots are no longer seen. Once the full course of treatment is complete, the temperature must be lowered slowly back in the 68° to 75° Fahrenheit (20° to 24° Celsius) range and a new carbon placed in the filtration. UV sterilising filters can also treat Ich in well-established tanks and are less traumatic, but is most successful if integrated with smaller doses of medications or weaker medications (1/3 doses) and without raising the temperature too high (80° Fahrenheit or 26.7° Celsius) will suffice.

Other external parasites and fungal infection can be treated with loach-safe OTC medication. Hillstream Loaches with bacterial infections and skinny disease (Chronic Wasting Syndrome) must be quarantined and their tank treated with loach-safe antibacterial medication.

Where can I find Hillstream Loach for Sale?

The Hillstream Loaches that are sold in local shops and online stores are often bred and raised by expert Asian and Eastern European fish breeders. Some enthusiasts who are taken to this species will sometimes sell their fry after successful breeding and advertise it on popular sites such as eBay or fish keeping forums. Hillstream Loaches remain the most popular loach species to purchase and despite their vulnerable status in the wild, with their natural habitats being destroyed due to human activity, they are readily available for sale. It is important that fish keepers realise how taxing shipping is for Hillstream Loaches that may arrive in a poor state, which can be exceedingly hard to fix.

Hillstream Loach Price

Hillstream Loaches are sold as juveniles, with each priced from $13 to $15. Shipping costs may apply and the fees will increase depending on where a buyer lives.

Reticulated Hillstream Loach (Sewellia lineolate) vs Butterfly Loach (Beaufortia kweichowensis)

Butterfly Loaches are native to China, with some of their nicknames indicating this: Chinese Hillstream Loach; Hong Kong Pleco; Butterfly Hillstream Loach; Chinese Butterfly Loach and Chinese Sucker Fish. Although they both belong to the Gastromyzontidae family, they differ in genus and species with Hillstream Loaches being Balitoridae and Sewellia, compared to Butterfly Loaches that are Beaufortia and Beaufortia Kweichowensis. The Chinese Butterfly Loach is the most imported species of Loaches and is easily recognisable due to its yellow/gold colouration, which is disrupted with dark markings on both its body and fins. Their colouration darkens if they are stuck on a dark surface. Rather than belly-to-belly bursts of dominance, the Chinese Butterfly Loach will attempt to “top” the other by lying their body entirely on the other, which indicates that they have lost the fight. The Chinese Butterfly Loach’s sexual dimorphism can be observed by one difference: their colouration, where the males have stronger pigmentation compared to the females. The Chinese Butterfly Loaches has not been bred in captivity and there is very little information on their mating practices, thus any that are for sale are usually wild-caught.

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With decades of collective fishkeeping experience, we are happy to share the fish care tips that we've picked up along the way. Our goal at Fish Laboratory is to keep publishing accurate content to help fishkeepers keep their fish and aquarium healthy.

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