Yunnanilus longibulla

Where they come from

Yunnanilus longibulla is a little stone loach from Yunnan, China. Think clear, cool, spring-fed creeks and lake margins with sandy bottoms, leaf litter, and scattered pebbles. They spend their time nosing through fine substrate for tiny critters. A lot of populations are very local, which is part of why they can be touchy in home tanks.

Setting up their tank

These guys do best in a long, low tank with gentle flow and tons of soft substrate to sift. They are advanced mostly because they hate unstable water and rough handling.

• Tank size: a 20-long (75 L) is the minimum for a small group, 30 inches of floor space is nicer
• Substrate: fine sand (sugar-grain size). Add a sprinkle of smooth pebbles and leaf litter
• Filtration: sponge filter + gentle spray bar or pre-filtered HOB. High oxygen, not blasting current
• Temperature: 18-22 C (64-72 F). Briefly up to 23-24 C is ok if oxygen is high
• pH and hardness: roughly neutral to slightly alkaline, pH 6.8-7.8, 3-12 dGH
• Lighting: subdued. Floating plants or shaded areas help them relax
• Lid: tight-fitting. They are sneaky climbers and jumpers

Set up the scape with line-of-sight breaks: rounded stones, wood, and clumps of java moss or Cryptocoryne. I like a couple of leaf piles (oak or catappa) because they hold microfauna the fish pick at.

Keep the tank mature. Do weekly 20-30% water changes and vacuum lightly so you do not collapse the micro-life in the sand. Pre-filter sponges on intakes save a lot of tiny lives (and keep the loaches from exploring the filter).

What to feed them

They are micro-predators. Mine woke up for live and frozen foods and took ages to accept anything dry.

• Live/frozen: baby brine shrimp, daphnia, cyclops, bloodworms (chopped if large), blackworms
• Prepared: high-quality sinking micro-pellets, crushed shrimp pellets, Repashy gel (Community or Soilent Green) spread thin and cooled
• Timing: feed smaller portions 2-3x per day at dusk or with lights dimmed

Target feeding helps. I use a pipette to lay a thin line of food along the sand so every fish finds some. Mix a few micro-pellets into the live food once they are eating strongly to train them onto prepared options.

How they behave and who they get along with

Quiet, bottom-focused, and much bolder in a group. Keep 8 or more. They shuffle through sand together and do little sprints between cover. Most activity happens in low light.

• Good tankmates: small, calm midwater fish that like cooler water - white clouds, small rasboras (chili are ok if temps are moderate), ricefish, celestial pearl danios
• Also fine: small snails, larger shrimp species (they may eat shrimplets)
• Avoid: big or boisterous fish, fast danios that hoover food, cichlids, crayfish, or anything that needs strong river flow

Breeding tips

They scatter eggs in fine substrate and plants. No parental care. It is doable, but you have to protect the eggs.

• Condition adults with lots of live/frozen food for 2-3 weeks
• Set up a separate 10-15 gallon with sand, a thick moss mat, and a layer of marbles or mesh so eggs fall out of reach
• Cool, fresh water changes can trigger spawning. Slight dip to 18-20 C followed by steady feeding worked for me
• Remove adults after 2-3 days of chasing and resting cycles
• Eggs hatch in ~2-3 days at 20-22 C. Fry need infusoria/green water first, then microworms and baby brine as they size up

Common problems to watch for

• Heat and low oxygen: above 24 C they start stressing. Add surface agitation and keep temps down
• Barbel wear: rough or dirty substrate will erode barbels. Use fine sand and keep it clean but not sterile
• Internal parasites: wild fish often arrive with worms. Quarantine and consider a deworming regimen (e.g., praziquantel/levamisole) before they go into the display
• Refusing dry foods: mix micro-pellets into live food and be patient. Target feed
• Jumping: any gap is an exit. Cover cables and tiny openings
• Medication sensitivity: avoid copper- and formalin-heavy treatments. Use gentler options and lots of aeration if you must medicate

If you keep the water cool and oxygen-rich, use sand, and make sure they are actually getting food, Yunnanilus longibulla is a really rewarding oddball. They will never be the flashiest fish in the room, but watching a relaxed group sift and explore is great.