Hillstream Loaches: Care Guide for Fast-Water Tanks

If there's one fish that was made for a river tank, it's the hillstream loach. These flat, spotted little fish look like tiny stingrays stuck to the rocks, and they live in fast, shallow mountain streams in Asia where the water never stops moving. Give them that kind of water and they're hardy, busy and fun to watch. Keep them in a calm community tank and they struggle.

Which fish are "hillstream loaches"?

The name covers several related species sold in the hobby. The two you'll see most often:

• Reticulated or tiger hillstream loach (Sewellia species): small, flat, with bold spots or stripes.
• Butterfly or Chinese hillstream loach (Beaufortia kweichowensis and relatives): a bit larger, with wide fins that make it look like a little flying saucer.

Both are built the same way: a flat belly and fins that work like a suction cup so they can grip rocks in strong current.

Water temperature

Hillstream loaches like it cool. Aim for about 65–75°F (18–24°C). They tolerate a few degrees either side, but warm water holds less oxygen, and above about 77°F they get stressed. That makes them a poor match for tropical fish that want 80°F. In many homes they need little or no heater at all.

Flow and oxygen: not optional

This is the part people get wrong. Hillstream loaches need strong flow and lots of oxygen. A common guideline is total flow of about 8 to 10 times the tank's volume per hour, plus surface agitation. In still or gently moving water, they can slowly suffocate.

Good ways to get there:

• A powerhead or wavemaker aimed along the length of the tank
• A canister or hang-on filter with strong output
• An air stone or a filter that splashes the surface
• A river manifold setup, which creates one-way flow from end to end

Tank size and setup

A 20-gallon long can work for a small group of the smaller Sewellia, but 30 gallons or more is better, especially for butterfly types or a mixed tank. Length and bottom area matter more than height.

Set it up like a stream bed:

• Smooth river rocks and pebbles of different sizes
• Sand or fine gravel between them
• Driftwood, prepared properly (see preparing driftwood)
• Hardy plants tied to rock or wood, like Java fern and Anubias
• A tight lid. They can climb glass.

Feeding

In the wild, hillstream loaches graze biofilm and algae off rocks all day. In a new, spotless tank, they can go hungry. Add them to an established tank with some algae on the rocks, and supplement with:

• Algae wafers and sinking vegetable foods
• Frozen or live foods like bloodworms and brine shrimp
• Repashy-style gel foods spread on a rock

Watch their bellies. A sunken belly means they aren't getting enough.

Tank mates

They're peaceful and stay on the bottom and glass. Good company: other cool, fast-water fish such as White Cloud Mountain minnows, danios, some rasboras, and peaceful shrimp. Avoid big, aggressive fish and anything that needs warm, still water. They do best in a group of three or more of their own kind; they'll squabble a little, but it's mostly harmless.

Bottom line

Cool water, fast flow, lots of oxygen and rocks covered in biofilm: get those four right and hillstream loaches are one of the most rewarding fish for a river tank. They're the reason a lot of hobbyists build one in the first place.

Sources (3)

Aquarium Breeder: Butterfly hillstream loach care; Beaufortia kweichowensis, Wikipedia; AquariumStoreDepot: High-flow, cool-water requirements.

Related: Kuhli Loach Care in a River Tank