Hillstream Loach: Species Profile

Category: Loach

Common Names: Hillstream Loach

Scientific Name: Sewellia lineolata

Family: Balitoridae

Minimum Tank Size: 55 Gallons

Care Level: Moderate

Temperament: Peaceful

Max Size: 3 Inches

Temperature: 65-75 F

pH: 6.5-7.5

Tank Level: Bottom

Colors: Black, Brown

Diet: Omnivore

Breeding: Difficult

By Spiketooth [CC BY-SA 3.0]

Hillstream Loach Species Overview

The hillstream loach is a popular tropical fish because of its unique sprawling fins that give it the appearance of a freshwater stingray. These algae eaters are also excellent for helping to keep a tank clean.

Caring for hillstream loaches is easy, making them an excellent fit for beginners.

But it’s still important to offer your loach the proper tank conditions. We’ll teach you how so that they can enjoy a long and healthy life.

Distinguishing Features

Hillstream loaches look like a cross between a stingray and a catfish. But luckily, these fish don’t have a stinger, nor do they belong to the catfish family.

The most striking feature of hillstream loaches is their fins. Both their pectoral and pelvic fins span out in a wing-like fashion and overlap each other.

Aside from these fins creating a unique appearance in a tropical tank, they help hillstream loaches manage the strong currents they encounter in the wild.

Other features that allow these loaches to remain in place in the face of fast currents include a flat belly that lets them press up against rocks and a sucker mouth for grip.

Hillstream loaches share the same primary colors and patterns. They include:

  • A gray to yellow base color
  • Black stripes in several directions
  • Linear stripes on caudal and dorsal fins

Aside from the caudal and dorsal fins, the stripes on a hillstream loach are shorter and go in so many different directions that it forms the appearance of dots of varying sizes across this fish.

Looking closely, you can also see small barbells protruding from this fish’s head, which is why people sometimes mistake them for a catfish.


Hillstream loaches hail from Southeast Asia, mainly freshwater rivers and streams in Vietnam, Cambodia, and Laos.

They live in cooler, fast-moving water. Because of their body’s design, they can withstand intense river rapids, and they enjoy the abundant oxygen that such water brings.

These loaches prefer clear water and live in areas with lots of algae on rocks and plants growing from the substrate. Examples include java moss and anubias barter.

Hillstream loaches live in substrates that are a combination of sand and rocks of all sizes. These fish are active in the wild, living on and searching for food scattered on the substrate.

Hillstream Loach on White Background


Hillstream loaches are a small species, only growing up to two to three inches as adults. In the wild, they enjoy moving between small rock crevices, and you can expect them to do the same with hiding spaces in their tank.

But hillstream loaches enjoy being active, so you don’t have to worry about this small species always being in hiding.

Of the two genders, female hillstream loaches are girthier. They also have a broader head that blends almost evenly with the pectoral fins.

In contrast, males have a narrower head that gives them a smaller appearance, although there’s rarely a difference in length between the two sexes.


Hillstream loaches have a lifespan of eight to ten years. That’s an exceptionally long time for a tropical fish in captivity.

A combination of genetics and fish keeper care will determine your fish’s ultimate lifespan.

For this reason, it’s crucial to follow the guidelines we’ll be sharing soon for the correct tank and water parameters.


It can be hard to tell male and female hillstream loaches apart until they’re adults.

But once they reach sexual maturity, you’ll be able to decipher the two because females have rounder bodies. They also have a wider head that blends almost evenly into the rest of their body.

In contrast, males have a more distinct neck that separates their head from their pectoral fins and the rest of their body.

Even so, these differences aren’t huge.

So, if you have a group of hillstream loaches of the same gender, an untrained eye might have trouble determining whether you’re looking at males or females.


Hillstream loaches are peaceful fish that enjoy going about their business without bothering their tankmates.

That said, male hillstream loaches will sometimes fight each other, particularly if they don’t have enough space or hiding places in the aquarium.

The good news is that male hillstream loaches rarely injure each other when they get into a fight. Instead, they tend to battle it out by circling each other.

Ideally, you should purchase a group of three or more hillstream loaches since these fish enjoy being social with each other. But buying only two loaches is a bad idea, given that one fish may dominate the other for food and territory.

Despite these details, the reality is that fish keepers can feel at ease adding hillstream loaches to their current aquarium. These fish are often more concerned about sticking to the sides of the tank and eating algae than interacting with other fish.

Tank Parameters

If you’ve decided that hillstream loaches are the right fit for you, it’s time to set up a tank for them. We’ll explore the water conditions and physical aspects of preparing a tank that’ll keep your fish in tip-top shape.

Minimum Tank Size

We recommend purchasing a 50-gallon tank per three to four hillstream loaches.

Although hillstream loaches spend much of their time attached to rocks or the side of the tank as they eat algae, they enjoy moving around.

They also require plenty of hiding spots. So, a large tank will allow you to include lots of decorations and plants.

Water Parameters

Below are the water parameters that hillstream loaches need to stay healthy.


Hillstream loaches prefer their water on the cool side for tropical fish. Therefore, you should keep the water between 68°F and 75°F.

If other tank mates allow for it, it’s ideal to keep the temperature closer to 68°F.


Hillstream loaches prefer well-oxygenated water with a pH between 6.5 to 7.5. That’s a smaller pH range than many other fish species can tolerate, so we recommend testing their water often to ensure the pH remains okay.

When possible, keeping the water at a neutral 7.0 will make them the happiest.


Hillstream loaches are freshwater fish, so they don’t need salt in their tank.

But if your loaches come down with an illness, you may need to add aquarium salt to their tank. Salt is often effective in helping to treat parasitic, bacterial, and fungal infections.

Tank Setup

Arranging the proper water conditions in your hillstream loach’s tank is vital, but it’s equally important to set up the physical aspects of their aquarium to make it comfortable and appealing to them.

Below are the must-knows of doing so.


Using a fine sand substrate is best for hillstream loaches. That will mimic the base substrate they have in the wild.

But sand is also beneficial because you won’t have to worry about your loaches cutting themselves on it since they’ll spend so much time swimming along it.


The best decorations for hillstream loaches are rocks. You’ll want to choose smooth stones to avoid injury.

When arranging the rocks in your tank, keep in mind that your loaches will likely spend lots of time eating the algae on them and sleeping within them.

So, set up the rocks at angles that will give you the best view to observe your fish.

Since hillstream loaches stay at the bottom of their tank most of the time, there’s no need to worry about decorating the middle and upper portions of their tank (unless you want to, of course).


Live plants are an excellent addition to hillstream loach tanks.

Hornwort is a great choice, given that it grows up from the substrate, mimicking the environment that your loaches would have in the wild.

Java moss is another popular option for including in hillstream loach tanks.

In addition to creating a food source for loaches, plants also give them additional hiding places.


A standard aquarium light tank is sufficient for hillstream loaches.

Whereas most of the hundreds of species of loaches are nocturnal, the hillstream variety is diurnal. Therefore, they enjoy being active during the day, and a light will help their circadian rhythm know when it’s daytime.

That said, it’s equally important to have no light at night.

Therefore, purchasing an aquarium lamp with an automatic timer is ideal so that you don’t have to worry about switching it on and off.


A filter is essential for your hillstream loach tank. Purchasing a filter conducive to your aquarium’s size is vital to ensure it works properly.

If you buy a filter that can’t handle the number of gallons in your tank, toxins will build up, and your loaches will likely become ill.

Due to their small size, narrow bodies, and curious nature, hillstream loaches sometimes crawl into filters.

That’s a dangerous situation for them. For this reason, you must keep the opening to the filter covered with filter media or a filter sponge.


A heater often isn’t necessary for hillstream loach tanks, which goes against the grain for most tropical fish.

As long as the air temperature in your home always remains between 8°F and 75°F, your loaches will thrive without a heater.

The fact that hillstream loaches like such cool temperatures make it difficult for them to be tank mates with many other species of tropical fish. But placing your loaches into a warmer tank will significantly reduce their lifespan.


Hillstream loaches are omnivores by nature, but they eat a primarily plant-based diet from the algae they find on rocks and the substrate.

That said, they’ll also eat small crustaceans they encounter, which offer them an added boost of protein.

Giving your hillstream loaches a varied diet is vital to their longevity. Some of the best foods to feed them include:

  • Sinking pellets
  • Algae wafers
  • Brine shrimp
  • Bloodworms

You can give your hillstream loaches brine shrimp and bloodworms in live or frozen forms.

Furthermore, placing blanched kale and spinach in their tank is another great way to give them some extra nutrients.

In the wild, naturally occurring algae is sufficient to sustain hillstream loaches for long periods. But although your aquarium will have some algae your hillstream loaches can eat, your tank will (hopefully!) be too clean for them to sustain themselves from it.

You should feed your hillstream loaches twice per day.

Determining how much to feed them takes some practice. But the rule of thumb is to let them eat as much as possible in two to three minutes.

Then, remove the remaining food the best you can. With time, you’ll get a feel for how much food your hillstream loaches can eat during that period so that you don’t have to “fish” out their leftover meal.


Unlike many species of tropical fish, it isn’t necessary to place hillstream loaches in a separate breeding tank as long as they don’t share their home with other fish species.

That’s because hillstream loaches won’t eat their eggs and babies.

Unfortunately, that’s where the easy part ends. Hillstream loaches tend not to breed well in captivity.

You’ll need to practice a lot of patience and carefully monitor the tank’s water parameters to ensure your fish have the ideal condition for breeding.

If and when the male and females become ready to mate, the male will dance around the female loach of his choice. With luck, she’ll accept his offer and stick by his side.

At that point, the male will start building a nest by digging in the substrate. You might want to add some extra sand at the bottom of the tank to ensure he has plenty of depth to do so.

Eventually, the female will release her eggs, and the male will fertilize them. Hillstream loach eggs take longer to hatch than many species of tropical fish, so you’ll need to wait a few weeks before seeing the baby fry in your tank.

Once you see the fry, add microworms, small live brine shrimp, and powdered fry food into the tank to ensure your baby hillstream loaches have plenty to eat.

Common Diseases

Hillstream loaches can fall ill to the same diseases as most tropical fish. Below are some of the most common conditions you may encounter.


Ich is a parasitic infection that is arguably the most common illness that hillstream loaches face. It occurs when your loach comes in contact with another infected fish.

Tiny white spots and itching against objects are the most common symptoms of ich in hillstream loaches.

You should immediately quarantine any fish showing signs of ich and begin treating the water with ich medication. Increasing the aquarium temperature—but not too much—is also effective.


Dropsy results from fluid accumulating inside your hillstream loach’s body, causing its belly to droop downward. They also might develop ulcers or protruding scales.

The most common causes of dropsy are unfavorable water conditions, dirty water, or an overcrowded tank.

Preventing dropsy is easier than treating it. However, immediately performing a water change and adding aquarium salt to the tank can help.

Hole-in-the-Head Disease

The Hexamita protozoan causes hole-in-the-head disease, which causes indented white hole-like lesions on a hillstream loach’s head.

Worm-looking mucus will often emerge from the holes in more progressive cases of this disease.

Treating hillstream loaches with metronidazole is the best way to eliminate hole-in-the-head disease. Luckily, mild cases of this illness don’t appear to affect fish negatively.

Fin Rot

Fin rot most often occurs from a dirty tank, allowing several strains of bacteria or fungus to enter your hillstream loach’s fins. It creates a stringy and white appearance to the fin tips.

The good news is that you can easily treat fin rot by changing a portion of their water and adding aquarium salt to their tank.

With time, most hillstream loaches are able to regrow their fins.

Popeye Disease

Popeye disease causes one or both of a hillstream loach’s eyes to bulge from their head. Their eyes may also develop a cloudy coating.

There are several causes of popeye disease, such as parasites and bacteria from poor water conditions.

Determining the cure for popyeye disease involves trial and error. An antibacterial medication sometimes works, while other situations require parasite medicine.

Potential Tank Mates

Hillstream loaches make excellent tank mates because they’re docile fish that keep to themselves. Furthermore, because of their small size, they don’t try to pick a fight with fish that are larger than them.

That said, since hillstream loaches would rather flee than fight other fish, it’s important to pair them with tank mates that are non-aggressive.

Furthermore, given that these loaches prefer cool temperatures, you’ll need to find companions that don’t require warm water.

So, taking these factors into account, some of the best tank mates for hillstream loaches include:

  • Danios
  • Rasboras
  • Goldfish

Remember, you should put a minimum of three hillstream loaches together in a tank.

And should you decide to add other tank mates with your hillstream loach, increase the tank size according to the number of gallons of water the other fish require.