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I think hillstream loaches are a super cool species, and interesting oddball that’s really fun to watch.

Simply to care for, this guide will walk you through everything you need to know about getting an aquarium environment right for hillstream loaches.

Quick Stats

• Care Level: medium
• Min. Tank Size: 40 gallons (151 liters)
• pH: 7.0-8.0
• Temperature: 65°-80°F (18°-27°C)
• Diet: omnivore
• Temperament: peaceful schooling fish
• Lifespan: 
• Size: 2.5 inches (6 centimeters)
• Family: Balitoridae
• How many can be kept together: can be kept as a single or as a group of four or more
• Scientific Name: Sewellia lineolata
• Common Name: reticulated hillstream loach

Hillstream Loach Species Profile

Hillstream loaches (Sewellia lineolata) are native to Thailand, Laos, Cambodia and Vietnam.

They can be found in fast-moving, clear mountain streams in that region. 

The current is often very, very strong in these waterways. The hillstream loach’s unique body shape lets it cling to rocks and driftwood so they can find food without being washed away by the current

Appearance

Hillstream loaches are one of the coolest looking fish in the hobby. I love them.

At first glance, they look like a teeny, tiny stingray. Their bodies are dorsoventrally compressed, meaning they are flattened from top to bottom, like stingrays and skates. They have large, rounded pectoral fins and smaller rounded anal fins that fan out from their bodies and hug the substrate. 

Viewed from above, they are vaguely shaped like butterflies with a slender trailing tail.

These fish have the neatest pattern of spots, speckles and stripes. The spots are a beautiful amber gold on a dark brown background, absolutely stunning.

Underneath their bodies, you’ll find their gill slits and their small scraping suckermouth that they use to eat algae, small crustaceans and biofilm. 

In the Aquarium

Hillstream loaches are a great addition to a tank’s cleanup crew. They’ll scoot around the tank eating algae, biofilm and sometimes uneaten food that’s gotten past your top-dwelling fish.

They’ll even move across the glass to munch on algae there. 

On the glass you can see their peculiar movement really well. They shuffle along in a back-and-forth motion that looks almost as if they’re walking on their fins. It’s really neat.

Hillstream loaches are very peaceful fish. They will get into little squabbles amongst themselves, but they don’t hurt each other.

This species can be kept as either a single fish or as a group of four or more. Don’t get just a pair as one fish will just constantly dominate the other.

They much prefer to be kept in a group, the more, the merrier.

How to Set Up a Hillstream Loach Tank

Tank Size

Although these are small fish, I recommend that you keep them in at least a 40 gallon (151 liter) tank. This will ensure that they have enough surface area to feed on.

If you want to keep a breeding colony, I’d recommend a 55 gallon (208 liter) to give everyone lots of room.

Filtration

This species can be very sensitive to poor water quality, so proper filtration is an absolute must.

Filters don’t just pump water around the aquarium, although this is important, filters actually do much, much more.

Inside of filters, there is special media (called biomedia) that houses beneficial bacteria that help break down fish waste.

Fish constantly poop and pee into the water around them, gross, but true. 

As that excrement breaks down, it puts off highly toxic ammonia. All it takes is 1 drop of ammonia in 13 gallons (50 liters) of water to start to stress and even kill fish. Just one drop in 13 gallons!

This is where filters come in. The ​​beneficial bacteria in the filter media eat ammonia and transform it, first into nitrite (also highly toxic) and then into nitrate, which can safely be allowed to build up in between water changes. 

This is known as the Aquarium Nitrogen Cycle. 

Without a filter, ammonia will just build and build in a tank until the water is completely toxic.

And I’d advise to add on extra filtration if you plan on keeping hillstream loaches. 

These little guys are very sensitive to water quality. Adding on extra filtration, like putting in an extra sponge filter, will make sure there is plenty of beneficial bacteria to process fish waste. 

They also need a lot of water flow. The hillstreams that these fish are named for, by their very nature, are fast moving waterways. 

It’s best to mimic this as much as possible in the aquarium. 

Hillstream loaches often congregate in the area of the tank that has the highest water flow.

I highly recommend putting in at least one powerhead in order to move more water around the tank. 

For more information about powerheads, please see our comparison article.

Water Parameters

• Temperature: 65°-80°F (18°-27°C)
• Ammonia/Nitrite: 0
• Nitrate: <30 ppm
• pH: 7.0-8.0
• GH: 3-15 dGh
• KH:  3-70 dKH

Heater

Hillstream loaches can tolerate a wide variety of temperatures: 65°-80°F (18°-27°C). 

They’re actually more susceptible to infection at higher temps, so keeping them in an unheated tank can sometimes be beneficial.

Colder water is more oxygen rich, making respiration easier for fish, and helping to boost their immune system. 

This species can still thrive in tropical temperatures, but I’d recommend keeping the tank at as low a temperature as you can. And make sure to add on lots of oxygenation and water flow to help support their respiration. 

Substrate

This species does scoot across the substrate quite a bit and their skin and fins are somewhat  delicate. 

Sand would be my first choice for substrate in this case. Smooth, rounded gravel could also work well.

I would recommend avoiding sharp or rough substrates, like Seachem Flourite. All those jagged edges and sharp points could potentially scrape the loaches’ skin, making them more vulnerable to infection.

If you plan on breeding hillstream loaches, they will do best on a sand substrate. The male loach will dig a small pit in the substrate for the female to lay her eggs in. This is more easily down on with a sand substrate.

Lighting

This species doesn’t really have any specific needs when it comes to lighting. You can just use whatever works best for your plants and/or viewing pleasure.

Plants and Decor

Hillstream loaches are grazers that scoot around all day, munching algae along the surfaces or rocks, plant leaves and sunken logs.

It’s best to try and recreate a river-like environment with a wide variety of hardcore elements that they can graze on. These fish will appreciate lots of smooth stones. 

They will often have little mock territorial battles over rocks. So, making sure there are lots of options in the tank will make sure each fish has a place to hang out.

Driftwood pieces add to the natural look of the tank and provide a great substrate for biofilm to grow on.

These fish will do some grazing along broad plant leaves, but they won’t destroy the plants at all. 

They’ll also hide in bushy, dense plants, like Java moss, if they feel threatened. 

This species isn’t the best at keeping algae off plants (that would be otocinclus catfish) but they will help keep it at bay.

Overall, just make sure that these guys have lots of surface area to graze on and a variety of hiding spots and they will be very happy. 

Hillstream Loach Diet

These little fish eat mostly algae, but they are omnivores that will also eat some meaty foods.

Because this species relies so much on eating algae, I would recommend that you only add them to an established setup that already has a good bit of algae growth.

These fish could starve if they’re placed in a brand new setup that doesn’t have much algae or biofilm growing in it.

To supplement the algae they eat, you can offer them some blanched veggies, like spinach, romaine or zucchini. Once the veggies get nice and soft, the loaches will happily devour them.

You can try to offer them some commercially made foods, but it may have mixed results.

I’ve seen some that will happily eat sinking wafers, and others who couldn’t care less. 

Hillstream Loach Breeding

These fish will readily breed in an aquarium, as long as they are happy and healthy.

Your best bet is to get a group of six or more to ensure that you get at least one male and female pair.

Content hillstream loaches will spawn every few weeks.

Keeping up with water changes and making sure that the water parameters stay on par is essential.

If you plan to breed hillstream loaches, I would recommend keeping them on a sand substrate. When the male and female fish pair up, the male will dig a small pit in the sand where the female will lay her eggs. 

There is no two separate the fry from the adults. These fish will not eat their own babies.

Hillstream Loach Tank Mates

Hillstream loaches are very peaceful little fish. They will tussle with each other a little bit, but they don’t actually harm each other at all.

They are best paired with other peaceful community fish.

If you want to keep them in an unheated aquarium, I would recommend pairing them with fish like zebra loaches and white cloud mountain minnows that can also thrive at lower temperatures.

Definitely, do not put them in a tank with any aggressive or semi-aggressive fish, like most cichlids.

Also, even if they are peaceful community fish, do not mix these fish with other bottom feeders since this will increase competition for food and territory.

Is a Hillstream Loach Right for You?

I think hillstream loaches are a super cool little species, an adorable and interesting oddball that’s really fun to watch.

They’re not hard to keep up with as long as you are keeping up with your aquarium maintenance so your water is healthy.

This species breeds readily, so you may need to find an outlet for fry.

If you have large and/or aggressive fish, this is not the right species. But, they’ll do just fine with other peaceful, small fish.

Just remember they do need a lot of water flow, so think about adding on an extra powerhead to keep the water moving.

I hope you find this article helpful.

I wish you and your fish the very best!