Bajiang Yunnan loach

Where they come from

Bajiang Yunnan loaches (Yunnanilus bajiangensis) come from Yunnan, China - cool, clear streams with a steady push of water over rock and gravel. Think hillstream vibes, but in a smaller, more "creek fish" package. Most of the ones you see in the hobby are wild-caught, so they show up already used to high oxygen and clean water.

Setting up their tank

These guys are why I call the species "expert." They are not forgiving of stale water, low oxygen, or a dirty substrate. Give them a tank that feels like a stream: lots of flow, lots of gas exchange, and plenty of hiding spots right on the bottom.

• Tank size: 20 gallons long is a nice starting point for a small group. Bigger is easier because it stays stable.
• Group size: keep at least 6 if you can. Singles hide and waste away in my experience.
• Substrate: fine gravel or sand with rounded pebbles. Skip sharp stuff - they spend their life on the bottom.
• Hardscape: smooth stones, cobbles, and some wood roots. Make little caves and crevices.
• Plants: optional. If you want plants, go for stuff that tolerates flow (Java fern, Anubias, Bolbitis, moss).
• Flow and oxygen: a strong filter plus a powerhead or wavemaker. Aim for visible surface ripple across most of the tank.
• Temperature: cool to moderate (roughly mid-60s to low-70s F / 18-23 C). They do better cool than warm.
• Water: neutral-ish is fine, but clean matters more than chasing a number. Keep nitrates low.

What to feed them

They are small, bottom-oriented micro-predators and pickers. Mine spent all day pecking at biofilm and tiny critters on rocks, then went nuts for small meaty foods. If you feed only big flakes that stay at the surface, you will slowly starve them.

• Staples: sinking micro pellets, small wafers that soften fast, and crushed high-protein pellets.
• Frozen: cyclops, baby brine shrimp, daphnia, finely chopped bloodworms (not huge chunks).
• Live (great if you can): grindal worms, microworms, baby brine shrimp, small blackworms.
• Natural grazing: let some rocks get a light coat of algae/biofilm. They will work it like little vacuum cleaners.

How they behave and who they get along with

They are peaceful and a little shy at first, but they get confident in a group. You will see short little squabbles over a favorite rock or feeding spot, but it is more posturing than damage.

Tankmates need to like similar water. Fast, cool-water fish work. Slow, long-finned warm-water fish are a mismatch.

• Good tankmates: other small stream loaches (carefully, not the hyper-territorial kind), small danios, white cloud mountain minnows, some small barbs that like current, hillstream-type species if the tank is built for them.
• Use caution: shrimp (adults often okay, babies may disappear), very tiny fish or fry (may get picked), boisterous bottom feeders that outcompete them.
• Avoid: warm-water community staples (many tetras/guppies if you run warm), big cichlids, aggressive loaches, anything that turns feeding time into a brawl.

Breeding tips

Breeding Yunnanilus in home tanks is possible, but it is not something I would call predictable. Most people who pull it off are basically doing a seasonal stream simulation: cool period, then warmer with heavy feeding and big water changes. Spawning is usually quiet - no flashy displays like you get with some danios.

• Start with a well-fed group (ideally 8-12) so you have both sexes.
• Condition with lots of small live/frozen foods for a few weeks.
• Trigger attempts: a slight temperature swing (cooler period then a gradual warm-up), followed by a big cool water change and strong flow.
• Spawning setup: fine-leaved plants/moss, or a pebble bed with gaps where eggs can fall out of reach.
• If you see eggs/fry: move adults out or move the eggs. They will snack if they find them.
• First foods: infusoria and very small live foods, then baby brine shrimp as soon as fry can take it.

Common problems to watch for

Most losses with this species come from slow, boring stuff: not enough oxygen, not enough food getting to the bottom, or a tank that is clean on paper but dirty in the substrate.

• Wasting away: often from competition or internal parasites in wild fish. Quarantine and treat if needed, and make sure they are actually eating.
• Gasping or hanging in high-flow areas nonstop: low oxygen or poor gas exchange. Add surface agitation and check for clogged filter media.
• Sudden deaths after a heat wave: they do not love warm, stale water. Fans, cooler room temps, and extra aeration help a lot.
• Bloat/constipation: too much dry food, not enough variety. Mix in daphnia and smaller meaty foods, and do not overfeed pellets.
• Ich and other external parasites: wild fish can carry stuff. Quarantine is your friend, and keep treatments loach-safe (they can be sensitive).