Hillstream Loach: What To Know Before Buying This Loach

Are you looking for a bottom dweller that is sure to steal the spotlight from any free swimming fish?

Well look no further than the Hillstream Loach.

These peaceful Loaches thrive in community tanks and will clean up your tank as they go. They make wonderful algae eaters.

In this article we cover everything you need to know, from tank mates, to popular varieties, and much more…

Hillstream Loach


The Hillstream Loaches are a group of river loaches from the family Balitoridae.

They can all be found in the fast flowing rivers of Vietnam including Quang Nam, Thua Thien Hue, Laos, Binh Dinh and Quang Ngai.

When most people mention the Hillstream Loach they mean Sewellia lineolata. This is the most beautiful and popular Hillstream Loach.

This Loach will be the focus of this article. However, even if you are interested in keeping a different variety keep reading. Even though they have slightly different adaptations and appearances they all require similar care and water parameters.

They are popular because they are one of the best-looking bottom dwellers around. They are useful in maintaining algae levels whilst also getting along with many tropical free-swimming fish.

Although most are from the family Balitoridae, this loach is of the order Cypriniform and the superfamily Cobitoidea, which is split into a further 8 groups, Sewellia lineolata is from the Gastromyzontidae family.

Hillstream Loaches will live for between 6-8 years.

You can usually buy juveniles for around $15-20.

Key Facts:

  • Experience Required: Advanced.
  • Nicknames: Tiger Hillstream Loach, Reticulated Hillstream Loach.
  • Color Forms: Light brown with white spots.
  • Size: 2.5-3 inches.
  • Tank Size: Minimum 50+ gallon.
  • Tank Temperature: 68-75°F.

  • Clean up algae
  • Fascinating to watch as they latch onto the substrate
  • Beautiful coloration and patterning
  • Compatible with many smaller tropical fish

  • Very difficult to breed
  • Require a large pump set up
  • Cannot tolerate spikes in water parameters
  • Shy in front of humans

Hillstream Loach Appearance

Sewellia lineolata

The appearance of the Hillstream Loach is what makes them so attractive to many in the fishkeeping hobby.

They look like a small stingray and have a remarkably streamlined body. Their body is encircled by a fan of wing-like pelvic and pectoral fins.

Their body shape is an adaptation to the very fast flowing rivers of Asia, where they suck onto rocks and allow water to pass swiftly over them.

They are relatively small in comparison to other Loaches and will reach 2.5-3 inches as an adult. Their size does not take away from their beautiful patterning. They have dark brown-black stripes embellished with lighter cream-yellow spots and wiggles. The patterning spreads to their pectoral, pelvic and caudal fins too.

There is something so captivating about the appearance of these fish. If their patterning and shape were not fascinating enough, their underside is something to behold.

Hillstream Loaches have developed a suction mechanism using their pectoral and pelvic fins which allows them to stick to rocks and the glass of aquariums whilst simultaneously feeding on algae.

If you are looking to distinguish the sex of your Hillstream Loach then all you need to do is look at the head and roundness of your fish from either above or from the underside.

Females have a rounder body with a wider head that looks as though it joins onto the pectoral fins. The males, on the other hand, have a slightly slimmer body and you may see some small tubercles develop along the head and on the first few rays of the pectoral fins called fences.

Size and Growth Rate

The Hillstream Loach grows to around 2.5 and 3 inches long.

However, they have a very slow growth rate.

Once fry have hatched it takes around 1 year for them to become fully grown. They reach the subadult status, where they are around 2-2.5 inches long, at around 7 months after hatching.

Common Varieties

In addition to Sewellia lineolata, there are two other very popular Hillstream Loaches:

  • Chinese Hillstream Loach (Beaufortia kweichowensis): The Chinese Hillstream Loach, or the Butterfly Loach, is a similar size and shape to the Tiger Hillstream Loach. They are more of a green color, with darker forest green spots that mirror a leopard’s spots.
  • Spotted Hillstream Loach (Sewellia sp. SEW01): The Spotted Hillstream Loach is very similar in appearance to Sewellia lineolata. They have an abundance of spots covering their entire body, head and all of their fins.

History and First Sighting

Sewellia lineolata was discovered roughly 180 years ago by Pierre-Medard Diard in Vietnam.

They were found in deeper pools of the fast-flowing rivers of Asia and they were also found in marginal rocky pools that were disconnected from the main river.

Sadly these Loaches remained largely unknown until their rediscovery in the 1990s.

They were introduced into the aquarium hobby in the mid-2000s and quickly became one of the most popular Loaches around.

Initially, they were the only species in the genus Sewellia, but there have been numerous additions since then including S.marmorata. Sewellia lineolata is currently considered vulnerable under the IUCN redlist primarily due to habitat destruction.

Hillstream Loach Care Guide

Hillstream Loaches

This fish is recommended for experienced fish-keepers only due to their required water conditions.

Because Hillstream Loaches do not have scales they are very susceptible to water spikes, sickness and chemicals.

The most important part of their care should be taken care of with the tank set up.

You should invest in a very good filter and pump that is capable of turning the water over 15 times per hour. This will give them a very fast flow and enough oxygenation whilst maintaining water purity. In addition to this 25% water changes should be made weekly, plus weekly substrate siphoning.

When it comes to diseases, the ones to look out for are any skin conditions and common freshwater diseases such as ich. Ichthyophthirius multifiliis is a parasitic ciliate that attaches itself to the external integument of the fish. This appears on the fish’s body as white spots and occurs due to poor water quality or the introduction of a new fish that already has ich.

The best way to treat Ich is by using over-the-counter medication which is often sold at fish stores, in addition to frequent water changes and siphoning of the substrate.

Another disease to look out for are fungal infections which arise due to bad water quality and infected wounds. They are characterized by fluffy, white-looking growths on the Loach.


In the wild Hillstream Loaches are omnivorous and enjoy eating algae biofilms and microscopic phytoplankton, bacteria and fungi, in addition to invertebrates such as zooplankton.

They also occasionally eat insect larvae.

You should try to replicate this in your aquarium.

The first step to take is making sure your set-up supports the growth of biofilm on large surface areas. You can do this by adding smooth rock surfaces and plants. Hillstream Loaches prefer soft, green algae, so you should avoid more rubbery-like algae such as Filamentous algae.

This soft green algae will act as a base diet for them, although you can add some other sources of vegetation such as kale leaves, cucumber and lettuce every now and then. You can also use algae wafers if your tank is not yet fully mature or you have a lack of biofilm growth.

Although they are omnivorous they do not need many protein-rich foods.

You can occasionally give them micro-crustaceans such as Daphnia, Thawed Bloodworms, Insect Larvae or Brine Shrimps. You can also feed them:

  • Zucchini
  • Lettuce Leaves
  • Kale Leaves
  • Cucumber Slices
  • Brine Shrimp
  • Bloodworms
  • Daphnia
  • Mysis Shrimp
  • Insect Larvae
  • Algae Wafers

You should avoid sinking pellets or flakes as the structure of their mouths will not allow the consumption of these foods.


The Hillstream Loach is very peaceful and you will rarely find them antagonizing other fish or each other.

They tend to stay by themselves and are just fine on their own.

Most of the time they will stay at the bottom of the tank and only venture higher up when they feel comfortable enough to suck on the glass of the tank. If your Hillstream Loach is not relaxed then they will hide away.

One interesting behavior to watch out for is when they tussle belly to belly with each other.

This is a territorial behavior done by the males to establish a territory. If this happens you can prevent aggression by providing plenty of space for them to establish their own territories with lots of hiding spots. Although they will never physically harm each other, this can cause a substantial amount of stress for the less dominant individual.

Habitat and Aquarium Set Up

In the wild the Hillstream Loach lives in very fast-flowing rivers in humid, subtropical Asian rainforests.

They suck onto smooth rocks, eroded down by the fast river waters, which allows them to climb upstream. The habitat is plain, with minimal vegetation and plenty of big rocks spread evenly throughout a sandy substrate.

The water is very high in oxygen content due to the high water flow so you will need to set up a tank that replicates these conditions as closely as possible.

Aquarium Conditions

Hillstream Loaches will need at least a 50 gallon tank.

This is often surprising to people, given this Loach’s small size. However, it is impossible to set up an appropriate intensity of water flow in a tank smaller than this. You must use a bigger tank that is preferably longer in length giving a larger surface area for your loaches.

You will need to invest in a powerful filtration pump, ideally one that can pump and replenish your water more frequently than 15 times per hour. This is the most important part of the Reticulated Hillstream Loach setup as they require fast-flowing, well-oxygenated waters without impurities.

As for water conditions:

  • pH at a range of 6.5-7.5
  • Water that is highly oxygenated
  • Cooler waters of 68-75°F
  • Water hardness should be at around 10-12dGH

The trick to keeping these fish happy and healthy is to invest in test kits due to their sensitivity to changing water parameters. When using the test kits, you must ensure that ammonia levels remain at 0ppm, and nitrate never goes above 20ppm. In addition to this you want to be changing the water level 25% each week to retain high water quality.

You will need lighting high enough to encourage algal growth in your tank as this will serve as a food source for your Loach (40-watt tubes are ideal).

Fine-grained gravel or sand is the ideal substrate for these fish as they like to burrow and wiggle across the bottom of the tank. You should also place smooth pebbles or rocks on top of the substrate. These areas contribute to the total surface area that biofilms can grow on.

A planted tank is recommended as they reduce the nitrate content, increase oxygenation and again, provide surface area for biofilms to grow upon. Your Hillstream Loach will also appreciate the extra hiding spots. Some great plant options include Hornwort, Java Moss, Water Wisteria, Crinum and Anubias.

Tank Parameter Requirement
Minimum Tank Size 50 Gallons
Tank Type Freshwater
Temperature 68-75°F
pH 6.5-7.5
Hardness 10-12 dGH
Flow Heavy
Substrate Fine sand or gravel

What Size Aquarium Do They Need?

The Hillstream Loach will need at least a 50 gallon aquarium.

Each additional Loach should be given at least 10 gallons.

Tank Mates

The Hillstream Loach is a very peaceful community fish that often keeps to itself due to its small size and bottom-dwelling nature.

Because these Loaches need colder waters you cannot keep them with many freshwater tropical fish. That being said, there are a few compatible fish, including:

Tetras, Danios and Rasboras are perfect tank mates for Hillstream Loaches as they occupy the middle and top of the water column.

You should stick to smaller, peaceful companions. If you are looking to add some diversity then snails and shrimp are great options, especially as your tank should already be set up to encourage biofilm growth.

Avoid larger and aggressive fish such as Cichlids and aggressive Barbs.

They do not do well in tanks with lots of other loaches as this will lead to spats over territory and food.

Keeping Hillstream Loaches Together

You can either keep Hillstream Loaches on their own or in groups of 3 or more.

Keeping them only in a pair can lead to one outcompeting and bullying the subordinate, which is an unhealthy dynamic.

If you decide to keep a group of Reticulated Hillstream Loaches, make sure to give them enough space to establish a territory as well as plenty of hiding spaces. A group of 4 will need at least 80 gallons.

Breeding Hillstream Loaches

Hillstream Loaches are notoriously difficult to breed in home aquariums.

However, it is possible under the right conditions and with a separate breeding tank.

You will need a 50 gallon tank with a strong pump.

Once you have selected a healthy male and female for breeding you can place them in this separate tank and raise the temperature to 78°F. It is important to retain all other water parameters and decorations exactly the same as their regular tank.

You should add plenty of smooth pebbles as the female is more likely to deposit eggs if there is a safe environment for her to do so.

After raising the temperature slightly, perform a cool 25% water change. You can also feed them high protein foods such as Brine Shrimp to get them ready to mate.

You will know when the male is courting the female as he will follow and chase her around the tank.

The female may now choose to ignore the male and go about her business or she will stick by him while he digs in the substrate, forming a nest. If you see them making a nest then there is a chance the female will release her eggs into the nest and if this occurs, the male will fertilize the eggs with milt.

Hillstream Loach eggs are tiny and white or translucent, though some may be a little bit yellowish. The eggs are often deposited out of sight, usually among larger pebbles or rocks.

It takes two weeks before the fry will hatch and when they do you should feed them infusoria, microworms, powdered fry food or baby brine shrimp straight away. The fry should be just fine in the same tank as the parents but they should not be introduced to the main tank until they are matured as they are at risk of being eaten by bigger predators.

Because they are so difficult to breed in captivity the number of fry per clutch of eggs is unknown.

Species Summary Table

Hillstream Loach
Other Common Names: Reticulated Hillstream Loach, Tiger Hillstream Loach
Scientific Name: Sewellia lineolata
Family Name: Gastromyzontidae
Distribution: Vietnam
Size: 2.5-3 inches
Color: Light brown with white spots
Care Level: Advanced
Temperament: Calm and docile
Lifespan: 8-10 years
Minimum Tank Size: 50 gallons
Tank Mate Compatibility: Compatible with many smaller, peaceful fish.


The Hillstream Loach is perfect for a sandy-bottom tank stocked with peaceful fish.

They are best known because of their dazzling appearance and lack of aggression.

These Loaches can peacefully fill in that space at the bottom of your tank. One of the only downsides is that they are difficult to breed in captivity, though you may wish to take this on as a challenge.

All of these traits make them a wonderful addition to any peaceful community tank.

Let us know your questions in the comments below…