Vanmanenia gymnetrus (hillstream loach)

Where they come from

Vanmanenia gymnetrus is one of those true hillstream fish that comes from fast, cool, oxygen-packed streams. Think shallow riffles over rounded stone, lots of current, and biofilm growing on every hard surface. They are built for clinging to rock and grazing all day, not for cruising around a calm community tank.

Setting up their tank

The tank for this species is basically a river section: lots of flow, lots of oxygen, and a ton of grazing area. Fancy aquascape skills help less than getting the water movement and surfaces right.

• Tank size: I would not do them in anything under 20 gallons long, and bigger is easier. Footprint matters more than height.
• Flow: strong. A powerhead or a high-flow filter with a spraybar aimed down the length of the tank works well.
• Oxygen: aim for constant surface agitation. If the surface looks like a mirror, you are not there yet.
• Substrate: smooth sand or fine gravel, plus lots of rounded river stones and cobbles.
• Hardscape: stack rocks to create lanes of current and calmer eddies. They will use both.
• Plants: optional. If you use them, pick stuff that tolerates flow (Anubias, Java fern, Bolbitis) and attach it to rock/wood.

I like to seed the tank with extra rocks in a tub under a cheap light for a few weeks, then rotate them in. It keeps a steady supply of biofilm going, and the loaches spend more time grazing and less time begging.

What to feed them

They are grazers first. In a new, squeaky-clean tank they can starve with a full belly of nothing. Once you have mature surfaces, feeding gets way easier.

• Daily staples: aufwuchs/biofilm on rocks, algae wafers (small pieces), quality sinking pellets that soften fast
• Veg: blanched zucchini/cucumber (clip it down), spinach, or a little Repashy-style gel food if you use that
• Protein: frozen baby brine, daphnia, cyclops, and the occasional bloodworm (not as a main diet)
• Extras: powdered foods or crushed flakes blown into the current can help smaller/younger fish find food

Watch the belly line. A healthy hillstream loach looks nicely filled out from above, not pinched behind the head. If you see that "knife-edge" look, increase grazing surfaces and offer more frequent small feeds.

How they behave and who they get along with

Vanmanenia are generally peaceful, but they are not pushovers. They like their favorite rock, and you will see little shuffles, shoulder bumps, and short chases over grazing spots. Most of it is bluffing.

• Best tankmates: other current-loving fish like small danios, white clouds, hillstream minnows, and similar-temperature peaceful species
• With other loaches: usually fine if you give lots of rock surface and hiding breaks in the flow
• Avoid: big boisterous eaters that will outcompete them at feeding time, and warm-water fish that want the heater turned up

I have had the best luck keeping them in a small group so no single fish gets picked on, but not so many that every rock becomes contested. More surface area solves a lot of social drama.

Breeding tips

Breeding Vanmanenia in home tanks is possible but not something most people stumble into by accident. If you want to try, think seasonal: heavy feeding during a "cool" period, then a gradual warm-up and big water changes that mimic rains.

• Give them a mature, algae-rich tank and keep them well-fed for a couple months
• Add lots of crevices and smaller rounded stones where eggs could fall out of reach
• Try large, frequent water changes with slightly cooler water to simulate fresh stream flow
• If you ever see tiny fry, they need constant micro-foods and biofilm - they do not magically live off "the tank" in a sterile setup

Common problems to watch for

• Slow starvation: fish looks active but gets thinner over weeks. Usually a new tank, not enough grazing area, or too much food competition.
• Low oxygen/high heat stress: hanging in high-flow areas constantly, rapid gill movement, acting "restless". Increase surface agitation and reconsider temperature.
• Infections after shipping: scrapes and small sores can happen from rough handling. Keep water very clean and avoid strong meds unless you know what you are doing.
• Ich and other parasites: hillstream loaches can be sensitive to some treatments. Raise oxygenation during treatment and research dosage carefully.
• Poor flow layout: if all the current is a single jet, they get blasted and hide. Spread the flow with a spraybar or deflect it off hardscape.

If you get the river vibe right, they are pretty hardy day-to-day. Most losses I have seen were setup-related: not enough oxygen, not enough mature grazing, or being outcompeted at meals.