Discolored Yunnan loach

Where they come from

Yunnanilus discoloris is one of those little hillstream-adjacent loaches from Yunnan, China. Think cool, clean upland waters with steady flow, lots of stones, and not a ton of gunk sitting around. They are not the usual warm-community loach, and most of the trouble people have with them comes from keeping them too warm and too dirty.

Setting up their tank

Give them a long footprint more than a tall tank. They spend their time on and around the bottom, cruising over rockwork and picking at biofilm. A 20 gallon long works for a small group, but more floor space is always appreciated.

Flow and oxygen are the whole game. I have had the best results with a canister or strong HOB plus a big sponge filter, and a powerhead aimed along the back to make a consistent river-like loop. You want no dead spots where mulm just piles up.

• Substrate: smooth sand or fine rounded gravel (skip sharp stuff - they root and rest on the bottom)
• Hardscape: lots of rounded stones, small cobbles, and a few crevices they can duck into
• Plants: hardy, low-light options tied to rocks (Anubias, Java fern, moss) or just let algae/biofilm be a feature
• Filtration: oversized, with prefilter sponges so you do not puree baby food into the impeller
• Temperature: cool to mid-70s F is where I keep them comfortable; avoid pushing warm for long periods
• Water movement: noticeable current across the bottom, not just surface ripple

Cover the tank. They are not famous jumpers like some minnows, but startled loaches can and will find gaps. Also, keep your intakes guarded. They love poking into places they should not fit.

What to feed them

In my tanks they act like constant grazers that also appreciate meaty bits. If you only offer flakes once a day, you will have skinny, cranky loaches that never settle in. I feed smaller portions more often and aim for food that actually reaches the bottom.

• Staples: sinking micro pellets, small wafers, and gel foods they can pick at
• Frozen: cyclops, daphnia, baby brine shrimp, bloodworms (as a treat, not daily)
• Live: grindal worms, blackworms (if you trust your source), newly hatched brine
• Grazing support: let some rocks get a light coating of algae and biofilm, or rotate in a "seasoned" stone from another tank

Watch their bellies. A healthy group looks gently rounded, not pinched. If you see hollow bellies, it is usually not a mystery disease - it is usually food not reaching them, too much competition, or a tank that is too warm and low on oxygen.

How they behave and who they get along with

They are peaceful, a bit shy at first, and way more confident in a group. Once settled, you will see them doing little pecking runs over stones and sand, and occasionally squabbling in a harmless, loachy way over a favorite spot.

• Group size: 6+ is where they start acting natural
• Good tankmates: small cool-water minnows/danios, white clouds, other gentle hillstream-type species that like flow
• Avoid: big boisterous fish, warm-water community staples that want 78-82 F, and anything that will outcompete them at the bottom (large Cory groups can be too much in smaller tanks)

They are not plant destroyers. The only "damage" I see is them constantly rearranging fine sand around rocks, which is honestly part of the charm.

Breeding tips

Breeding is possible but not a set-it-and-forget-it project. Most success I have seen (and had) came from keeping a well-fed group in a mature, high-flow tank, then doing a series of cool water changes to mimic seasonal rain. Spawning is subtle - you usually notice because tiny fry show up later, not because you caught a big event.

• Start with a group and let them sort out pairs naturally
• Condition with lots of small live/frozen foods for a couple weeks
• Do several larger water changes with slightly cooler water (not an ice bath, just a noticeable cool-down)
• Add fine-leaved moss or spawning mops, plus rock crevices for eggs to end up in
• Keep intake sponges extra clean so fry do not get plastered to them

Adults may snack on eggs and tiny fry, so if you are serious about raising numbers, moving adults out or moving eggs/fry to a separate rearing tank gives you much better odds.

Common problems to watch for

Most losses happen early, right after purchase. These loaches tend to come in stressed and thin, and they hate swings. Slow acclimation, high oxygen, and a calm tank make a big difference in the first two weeks.

• Heat stress: hanging at the surface or sitting in high-flow only, acting lethargic, rapid breathing
• Low oxygen: gulping, clustering near filter outflow, sudden deaths after a warm day
• Skin/fin issues from poor water: frayed fins, red patches, excess slime coat
• Internal parasites: persistent hollow belly even though they eat (quarantine helps a lot)
• Starvation in community tanks: they eat, but never enough because food is gone before it hits bottom

Quarantine is worth your time with this species. I keep them in a simple bare-bottom QT with smooth rocks, a seasoned sponge filter, and strong aeration. Once they are eating aggressively and holding weight, they are much less finicky in the display.