Bailian cave loach

Where they come from

Bailian cave loaches (Yunnanilus bailianensis) are from cave and karst spring systems in Yunnan, China. Think cool, hard water moving through rock, lots of cracks and crevices, and not much in the way of plants. They are built for low light and tight spaces, and they act like it in the aquarium.

Setting up their tank

Start with stability and oxygen. I would not even attempt this species in a new tank. You want a mature setup with a biofilm-y feel to it and zero drama with ammonia or nitrite.

Tank size is less about swimming room and more about giving them territories and hiding. A 20 gallon long is a nice minimum footprint for a small group, but bigger is always easier because you can spread out flow and reduce spats.

• Temperature: cool to mild (I aim 64-72F). Short periods warmer usually bring problems.
• Flow: moderate to strong. They love current lanes.
• Oxygen: high. Surface agitation is your friend.
• Substrate: sand or fine gravel so they can root around without scraping themselves up.
• Hardscape: piles of rounded rocks, slate stacks, and lots of crevices. Build it like a little maze.
• Light: dim to moderate. They do not need bright light, and it tends to make them hide more.

Filtration wise, I like an oversized canister or hang-on-back plus a sponge filter for extra bacteria and backup. Aim the return along the length of the tank to create a steady run of current, and leave calmer pockets behind rockwork so they can rest.

Water chemistry does not need to be magic, but it does need to be consistent. They generally do well in neutral to alkaline, moderately hard water. If your water is very soft and acidic, you may have a tougher time long term unless you buffer it.

What to feed them

They are not picky once settled, but they can be stubborn at first. Mine did best with food that sinks quickly and lands in the rocks, because that is where they feel safe eating.

• Staples: sinking micro pellets, small wafers, and quality bottom-feeder pellets
• Frozen: bloodworms, daphnia, cyclops, brine shrimp, chopped blackworms (great for conditioning)
• Live (if you can): blackworms, grindal worms, small white worms
• Natural grazing: let some surfaces grow biofilm and aufwuchs - they will pick at it

Skip messy feeding. These are expert-level partly because they hate dirty water but also like rich foods. That combo means you have to be disciplined: smaller portions, more often, and keep your filter and substrate from becoming a sludge bank.

How they behave and who they get along with

They are secretive until they decide the tank is theirs. After that, you will see a lot more of them, especially at dusk and during feeding. They are not aggressive in a predator sense, but they do squabble over favorite cracks and caves.

Keep them in a small group if you can. Singles tend to stay hidden and spook easily. In a group, you get more natural behavior, and the timid fish learn the schedule from the bold ones.

• Good tankmates: other coolwater, current-loving fish that are not hyper (think small danios from cooler water, hillstream-type fish with similar needs)
• Avoid: warmwater community fish, long-finned slow fish, and anything boisterous that will outcompete them at feeding time
• Also avoid: big predatory loaches or catfish that will claim every cave

Breeding tips

Breeding is possible but not something I would call predictable. The main hurdle is getting them settled, well-fed, and seasonal cues that match what their bodies expect.

• Condition with varied frozen/live foods for a few weeks
• Cooler water and strong oxygenation seem to help
• A gentle seasonal swing (slightly cooler period, then a gradual warm-up within their safe range) can trigger activity
• Give them lots of tiny crevices and darker zones - they like to spawn where you cannot see it

If you ever find tiny fry, they will need microfoods right away. Think infusoria, powdered fry food, and baby brine shrimp once they are big enough. In a tank with lots of established biofilm, some fry can make it without you even noticing until they are suddenly there.

Common problems to watch for

Most issues trace back to three things: too warm, not enough oxygen/flow, or water that is getting dirty between maintenance days.

• Chronic hiding and poor feeding response: often too bright, too much traffic, or not enough cover
• Rapid breathing and hanging in flow: oxygen is low, surface agitation is weak, or temperature crept up
• Skin sores or red patches: usually from scraping on sharp decor or from deteriorating water quality
• Unexplained losses after "fine for months": slow heat stress or gradual waste buildup is a common pattern

One boring habit that saves these fish: do a quick weekly check of your actual tank temperature (not just the heater dial) and clean pre-filter sponges regularly. In high-flow, high-feeding setups, those sponges load up fast, and your oxygen and water quality drop before you notice.