Dojo Loach (Weather Loach) Care Guide

The dojo loach (or weather loach) is a big, eel-shaped, dog-tame coldwater loach with two traits that catch beginners out: it is a temperate, room-temperature/pond fish that should never be kept tropical long-term, and it is a relentless escape artist that needs a fully-sealed lid. Add a 25 to 30 cm adult size, a taste for snails and shrimp, and the famous barometric "weather" behaviour, and you have a characterful fish that simply does not belong in a heated nano community.

Dojo Loach (Weather Loach) at a glance

The sourced figures the welfare engine uses to judge Dojo Loach (Weather Loach) — the parseable key facts.

Where it comes from

It is a temperate East-Asian mud and ricefield fish, native from Siberia (the Amur drainage) and Sakhalin through Korea, Japan and China south to northern Vietnam. It lives in shallow, slow-moving rivers, swamps, oxbows, backwaters and paddy fields over soft mud and silt with dense vegetation — the opposite of a clear hill-stream. Every care decision follows from that origin. The temperate, seasonally cold habitat makes it a coldwater / room-temperature / pond fish that thrives unheated and tolerates cool water other community fish can't; sustained tropical heat is a welfare problem, not a target. The soft-mud ricefield bed makes it an obligate burrower needing a deep, fine-sand bed it can submerge into. The low-oxygen pond water gave it accessory intestinal air-breathing and extraordinary hypoxia, ammonia and drought tolerance — it can survive over 80 days of desiccation and near-freezing water. And the still-water origin means it wants gentle flow, not strong current.

Did you know?

• It predicts the weather — its namesake. Before storms or falling barometric pressure it swims frantically and may even stand or swim upright, hence "weather loach".
• It breathes air through its gut — in low-oxygen water it gulps air at the surface and uses its posterior intestine (and skin) as accessory breathing organs, so an occasional surface dash is normal, not distress.
• It can survive being frozen in ice — and months of drought. Critical thermal minimum around minus 1 to 2 degrees, surviving encased in ice, and it can withstand desiccation for more than 80 days by burrowing into damp mud. One of the toughest aquarium fish alive.
• By headcount it is the most farmed fish on Earth — a major food fish across East Asia (the Japanese dojo).
• It can clone itself — beyond normal spawning it reproduces asexually via gynogenesis, producing clonal and even polyploid lineages.
• It's a documented global invader — released aquarium fish have established wild populations across a dozen-plus US states plus Australia and Europe, so it must never be released.
• It plays and piles — grouped dojos rest together in heaps and chase each other playfully, an engaging, almost dog-like personality.
• A gold (and albino/pink) colour form exists alongside the wild brown-marbled type. IUCN lists it as Least Concern.

Tank size — and why

A 55 US gallon tank, at least four feet (120 cm) long, is the practical floor for a small group, and bigger or longer is better. The driver is adult size plus high activity plus full-length roaming plus burrowing floor area, not bioload alone: this is a 25 to 30 cm (10 to 12 in) active eel-shaped loach that uses the whole bottom, so floor length matters far more than height. Ignore the "6 inch" figure some quick-guides quote — that reflects young or stunted, short-kept fish. FishBase records 28 cm SL and Wikipedia up to 30 cm in the wild, and you should plan the tank for a 25 cm-plus fish, not a small one.

As a guide, a 55-gallon tank comfortably suits a starter group of about 3 Dojo Loach (Weather Loach). As floor-dwelling shoalers they want bottom area, not water column, so a bigger group or added tankmates pushes you toward a larger footprint rather than fitting in alongside.

How big does it really get?

Full-grown Dojo Loach (Weather Loach) reach about 25 cm (9.8 in) long, but they are usually sold at only about 5 cm (2 in) — a typical shop size (estimate). At full size, Dojo Loach (Weather Loach) needs roughly a 55-gallon tank, about 122 cm long; a common 10-gallon starter kit is only about 51 cm.

Adult size is sourced; the shop size is a typical-juvenile estimate; tank length is approximate for a standard 55-gallon aquarium.

Water parameters in practice

The headline is temperature: keep it unheated, at room temperature, roughly 16 to 22 degrees, with the cool end being where it thrives. FishBase records a temperate envelope of 5 to 25 degrees, and the invasive-species literature documents it surviving encased in ice down to minus 1 or 2 degrees — so it tolerates cold superbly and is harmed by heat, the reverse of the usual aquarium rule. Sustained tropical 26 to 28 degrees is a documented lifespan-shortener that can cut years off the fish; do not heat to tropical temperatures long-term. Aim for near-neutral, soft-to-medium water (pH about 6.5 to 7.5, tolerating 6.0 to 8.0) and it adapts well to typical tap water. Physiologically it is one of the hardiest aquarium fishes — extreme hypoxia, ammonia and drought tolerance — so it forgives water-quality slips better than most loaches, but that hardiness is a survival adaptation, not a licence to keep it badly; its real sensitivities are heat and sharp substrate.

Will it thrive in your water?

The comfortable range for Dojo Loach (Weather Loach) is about 16–24 °C (61–75 °F) and pH 6.5–8. Test your own tap water against it below.

These are the sourced comfortable ranges. Stable water matters more than chasing an exact number — a steady reading inside the band beats a "perfect" one that drifts. Some fish also need a particular water hardness (GH); where that applies, the prose above covers it.

Diet & feeding

In the wild it is a carnivore-leaning benthic omnivore, rooting through soft substrate for insect larvae, worms, small crustaceans, aquatic snails and detritus. Aquatic snails are a favourite, which is why it is used for pest-snail control — effective, but as with all snail-eating loaches not a guaranteed cure-all, and it still needs proper food. Feed sinking foods that reach the bottom: sinking pellets and sticks, algae and shrimp wafers, gel foods, plus live or frozen bloodworm, Tubifex/blackworm, brine shrimp, Daphnia and chopped earthworm for conditioning. It is a busy, enthusiastic, competitive feeder that scoops sand looking for food, so make sure the food actually reaches the bottom and is not eaten mid-water by faster tankmates. Because it digs constantly it readily finds buried leftovers, so avoid overfeeding — uneaten food fouls the sand.

Gear & setup

No heater needed — this is a coldwater fish kept at room temperature; if anything, a heated room may need watching at the warm end. A fully-sealed lid is mandatory: the dojo is a notorious escape artist that jumps and probes every gap, can survive out of water for hours, and will find any opening (filter cutouts, feeding flaps, cable holes must all be blocked). Substrate is more load-bearing than for most loaches: provide deep, fine sand at least 5 to 8 cm deep so the fish can fully burrow and submerge; sharp or coarse gravel shreds the barbels and abrades the soft, near-scaleless belly. Add hiding places, caves, driftwood and (sand-tolerant or potted) plants plus open sand to dig in. Keep flow gentle-to-moderate with good surface gas exchange — never a strong current. Note that while it makes a superb unheated temperate pond fish, outdoor stocking is restricted or illegal in many places because it is an invasive species.

Temperament & behaviour

Genuinely peaceful — one of the calmer, more sociable large loaches, not a fin-nipper or a bully of similarly-sized fish. The single exception is prey: it will eat eggs, fry and very small fish, so the peacefulness applies only to fish it can't swallow. It is crepuscular-to-diurnal and active once settled, far more visible than a kuhli, especially in a group and in cool water. Grouped dojos famously rest together in heaps and "chase each other playfully", giving them an engaging, almost dog-like personality. The standout quirk is the namesake "weather" behaviour: it becomes hyperactive, swimming frantically and even standing on end, before storms or drops in barometric pressure. Occasional dashes to the surface to gulp air are also normal intestinal air-breathing, not distress.

Group & social needs

Gregarious and happier in a group, though not an obligate tight schooler — it can technically survive singly, but a lone dojo hides more and is less confident. Keep three or more; bigger groups are bolder, more active and more visible. Unlike the yoyo loach there is no concentrated hierarchy-aggression to diffuse — grouping here is about confidence and activity, and grouped dojos simply pile up together and chase one another playfully.

Compatible tank mates (preview)

A short, engine-cleared shortlist — the species TankStocking's welfare engine clears with Dojo Loach (Weather Loach) and that suit its size and temperament best. Tap a name for its care guide, or use + to load the pairing in the planner.

• Bristlenose Pleco+Peaceful temperament, similar adult size
• Scissortail Rasbora+Uses the midwater zone, peaceful temperament, similar adult size
• Snakeskin Gourami+Uses the midwater zone, peaceful temperament, similar adult size
• Brilliant Rasbora+Uses the midwater zone, peaceful temperament
• Bronze Corydoras+Peaceful temperament
• Clown Pleco+Peaceful temperament
• Congo Tetra+Uses the midwater zone, peaceful temperament
• Croaking Gourami+Peaceful temperament

This engine-cleared shortlist is Dojo Loach (Weather Loach)'s tankmate surface for now — a dedicated tank-mates guide can follow for high-demand species.

Breeding & sexing

Rarely achieved in the home aquarium — captive-breeding reports are scarce and trade stock is largely farmed by hormone induction. (By individual headcount it is, remarkably, the most farmed fish in the world, as a food fish across East Asia.) It is an egg-scattering spawner — the male wraps his body around the female to stimulate egg release — with wild spawning seasonally temperature-cued. Sexing is subtle but real in mature fish: males have enlarged, more triangular/pointed pectoral fins (a thickened second ray forming a lamina circularis) and may show swellings behind the dorsal, while females are noticeably larger and fuller-bodied. As a shareable oddity, the species can also reproduce asexually by gynogenesis, producing clonal and even polyploid lineages. Home fry-rearing is essentially undocumented, so do not plan a breeding path.

Lifespan

Long-lived: typically 7 to 10 years with good (cool, clean) care, with documented specimens past about 15 years in well-maintained ponds and aquaria. The headline lifespan-killer is temperature — keeping this temperate fish too warm long-term causes chronic thermal stress and can cut the lifespan to just 4 to 5 years. Other shorteners: sharp gravel abrading the soft skin and barbels into infection; chronic poor water (despite its hardiness); overdosing harsh medications; injury from jumping out of an open tank; and being kept singly and stressed.

Common mistakes

• Keeping it tropical / heated long-term. The number-one welfare error. It is a coldwater / room-temperature fish; sustained 26 to 28 degrees shortens its life by years. If your tank is a heated tropical community, this fish does not belong in it long-term.
• Putting it with snails, shrimp or tiny fish. It eats snails, preys on dwarf shrimp and shrimplets, and will swallow fish or fry small enough to fit. Keep inverts or nano fish? Don't buy it (or buy it specifically to clear snails, accepting they'll go).
• Underestimating adult size and tank length. It reaches ~25 to 30 cm and roams the whole floor — a 10 to 20 gallon tank is wrong. Plan a 55 gallon-plus, four-foot-plus long tank from the start.
• No lid, or a leaky one. It is an escape artist and will find any gap; a fully-sealed lid is mandatory, and an open or gappy tank loses fish to the floor.
• Sharp or coarse gravel, or a shallow substrate. It burrows fully and needs a deep, fine-sand bed; sharp gravel shreds barbels and abrades the soft belly.
• Keeping just one. It is social; keep three or more for confidence and activity.
• Full-dose, copper-heavy medicating. Its soft, near-scaleless skin means conservative, loach-safe dosing, and the heat-cure for ich is awkward for a coldwater fish — prefer reduced-dose medication and modest temperature management.
• Releasing it outdoors. It is a documented invasive species (US, Australia, Europe) — never release unwanted fish; rehome them, and check local rules before any pond use.

Signs of trouble

• Staying buried or hidden constantly, even at dusk when a settled group should be active.
• Lethargy plus surface-gasping in a warm tank — a heat-stress warning (judge by context: an occasional gulp is normal air-breathing, but heat plus lethargy is a problem).
• Visible barbel erosion or belly/skin abrasions — almost always a sharp-substrate injury and a route to infection.
• Loss of colour and clamped fins.
• Emaciation or a hollow belly.
• A jumped-out fish on the floor — a sign the lid isn't fully sealed.

Is this fish right for you?

Do not buy dojo loaches if your tank is a heated tropical community; if you keep ornamental snails, a dwarf-shrimp colony, or nano fish and fry it could swallow; if you can't house three or more in a 55 gallon-plus, four-foot-plus long tank with a deep fine-sand bed and a fully-sealed lid; or if you wanted a small, tropical nano loach — this is a big, long-lived, coolwater, jumping, eel-shaped loach. Most dojos are farm-raised and hardy, so buy active, well-coloured, non-emaciated fish with intact barbels and quarantine new stock. The gold/albino "golden dojo" is a legitimate selectively-bred colour strain, not a dyed or balloon morph.

Bringing one home

Quarantine new dojos as good practice — they are hardy and mostly farm-raised, but the species has carried parasites such as Asian Gyrodactylus into new ranges. Acclimate them to a mature, cool, stable tank, and from the first day make sure the lid is fully sealed, because newly-introduced dojos are most likely to jump. Expect a new arrival to burrow into the sand and settle in over the first days.

Common questions

Is the dojo loach a coldwater or tropical fish?

Coldwater / temperate. It is happiest unheated at room temperature, roughly 16 to 22 degrees, and thrives at the cool end (it tolerates well below that, even near-freezing in a pond). Sustained tropical 26 to 28 degrees is a documented lifespan-shortener — do not keep it in a heated tropical tank long-term.

How big do dojo loaches get and what tank do they need?

About 25 to 30 cm (10 to 12 in) — ignore the "6 inch" figure some quick-guides quote, which reflects young or stunted fish. They are active full-length roamers, so plan a 55 gallon-plus tank at least four feet long, with length mattering far more than height, and bigger is better for a group.

Can I keep dojo loaches with snails or shrimp?

No. The dojo is a benthic invertebrate hunter that eats snails and preys on dwarf shrimp and shrimplets, and it will also swallow fish or fry small enough to fit. Treat snails, dwarf shrimp and nano fish as incompatible — keep it only with appropriately-sized, cool-tolerant tankmates.

Do dojo loaches jump?

Yes — they are notorious escape artists that jump and probe every gap, can survive out of water for hours, and are most likely to jump when newly introduced. A fully-sealed lid with every opening (filter cutouts, feeding flaps, cable holes) blocked is mandatory.

How many dojo loaches should I keep, and do they need sand?

Keep three or more — they are social, and grouped dojos are bolder, more active and pile up together to rest. They also need a deep bed of fine sand to fully burrow into; sharp or coarse gravel shreds their barbels and abrades the soft belly.

Why is my dojo loach swimming frantically or standing on end?

That is the famous "weather" behaviour — the dojo reacts to falling barometric pressure before storms with frantic or upright swimming. It is normal. Dashing to the surface to gulp air is also normal intestinal air-breathing, not distress.

Sources & confidence

Sources & confidence (9 species)

These back the Dojo Loach (Weather Loach) figures and the previewed tank mates above. Each figure is read from the TankStocking species database (v2026.06); below is the care reference behind it and how confident we are in that data. Confidence reflects the source quality, not whether any pairing is safe. Full source list and the welfare model are on the methodology page.

• Dojo Loach (Weather Loach) Misgurnus anguillicaudatus — Tankarium / aqua-fish.net (Misgurnus anguillicaudatus) medium confidence
• Bristlenose Pleco Ancistrus sp. — Aquarium Source / aqua-fish.net Ancistrus care guides high confidence
• Scissortail Rasbora Rasbora trilineata — Seriously Fish (seriouslyfish.com/species/rasbora-trilineata) high confidence
• Snakeskin Gourami Trichopodus pectoralis — Seriously Fish (seriouslyfish.com/species/trichopodus-pectoralis) high confidence
• Brilliant Rasbora Rasbora einthovenii — Seriously Fish (seriouslyfish.com/species/rasbora-einthovenii) high confidence
• Bronze Corydoras Corydoras aeneus — Seriously Fish (seriouslyfish.com/species/corydoras-aeneus) high confidence
• Clown Pleco Panaqolus maccus — Fish Laboratory (fishlaboratory.com/fish/clown-pleco); AquariumStoreDepot high confidence
• Congo Tetra Phenacogrammus interruptus — Seriously Fish (seriouslyfish.com/species/phenacogrammus-interruptus) high confidence
• Croaking Gourami Trichopsis vittata — Seriously Fish (seriouslyfish.com/species/trichopsis-vittata) high confidence

Care-guide sources (8)

This guide synthesises the references below; where they disagree, the range and the disagreement are noted in the text above. The figures in the key-facts box are read from the TankStocking species database (v2026.06). Full welfare model on the methodology page.

• FishBase — Misgurnus anguillicaudatus
• Seriously Fish — Misgurnus anguillicaudatus
• Wikipedia — Pond loach
• Tankarium — Dojo Loach
• aqua-fish.net — Dojo Loach
• USGS NAS — Misgurnus anguillicaudatus (Pond Loach) Species Profile
• Fish Laboratory — Dojo Loach Care
• Fishkeeping World — Dojo Loach Care Guide

More on Dojo Loach (Weather Loach)

Related guides on TankStocking — each scored by the same welfare engine as the planner.

This care guide is a sourced planning reference, not veterinary advice — individual fish, filtration and maintenance all matter. Cycle the tank, test your water, and observe your fish. How TankStocking works →