Why is my Weather Loach swimming wildly up and down the glass?

This is entirely normal behaviour. Weather Loaches are highly sensitive to changes in barometric pressure, and a sudden bout of hyperactive swimming often indicates an approaching rainstorm or a drop in atmospheric pressure. They also just enjoy playing in filter currents.

Can Weather Loaches live with Goldfish?

Yes, they make excellent companions for Goldfish in both large aquariums and ponds. They share similar temperature requirements and peaceful temperaments, though you must ensure sinking food actually reaches the loaches before the Goldfish eat it all.

Do Weather Loaches absolutely need a sand substrate?

Yes, a soft sand substrate is highly recommended. Weather Loaches naturally forage by sifting through the substrate with their delicate sensory barbels, and they love to bury themselves completely when resting or stressed. Rough gravel will cause injuries and painful infections.

Can I keep a Weather Loach on its own?

While they will survive alone, it is not recommended. They are highly gregarious fish that feel much more secure and display more natural, entertaining behaviours when kept in a group of at least three.

How cold can a Weather Loach tolerate outdoors?

They are incredibly cold-tolerant and can successfully overwinter in outdoor ponds in the UK. Provided the pond is deep enough (at least 60-90cm) so that it doesn't freeze solid at the bottom, the loaches will safely burrow into the sediment and enter a state of torpor until spring.

FreshwaterTropicalBeginner

Weather Loach

Misgurnus anguillicaudatus

The Weather Loach is a highly entertaining, eel-like coldwater fish famous for its erratic swimming in response to changes in barometric pressure.

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Ideal Conditions

Temperature: 10 – 25 °C
pH range: 6 – 8
Hardness: 5 – 20 dGH
Adult size: 15 – 25 cm
200L minimum for an indoor aquarium, or a well-filtered garden pond: 200 litres+
Lifespan: 7 – 10 years
Diet: Omnivore
Water flow: low to moderate
Preferred setup: Soft sand substrate is essential. Must have a tight-fitting lid indoors. Requires shallow margins and a deep overwintering zone if kept outdoors.

About the Weather Loach

Native to East Asia, the Weather Loach (frequently sold as the Dojo Loach) is a popular and exceptionally hardy species suited to both spacious unheated aquariums and garden ponds. They possess an elongated, cylindrical body equipped with ten sensitive barbels around the mouth, which they use to forage tirelessly in the substrate. Fascinatingly, they can gulp atmospheric air when water oxygen levels drop, absorbing it through their hindgut and expelling the remaining gas from their vent.

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Is it right for your tank?

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Where Weather Loach comes from

Native range

East Asia, Amur River basin

Countries / regions

China, Japan, South Korea, North Korea, Vietnam, Russia

Habitat

Slow-moving rivers, lakes, swamps, and flooded rice paddies with soft muddy substrates.

Widely introduced globally, including parts of Europe, North America, and Australia, where it is often considered an invasive species.

Similar species

Kuhli Loach
Pangio semicincta
Pond Loach
Misgurnus fossilis

We’re adding more full species guides as the catalogue grows.

Compatible tank mates

Reviewed guidance based on this species' recorded traits.

View all compatibility

Goldfish
Carassius auratus
Both thrive in similar coldwater or pond environments and have peaceful temperaments.
Great
White Cloud Mountain Minnow
Tanichthys albonubes
Excellent temperate tank mates that occupy the upper water column and tolerate the same cooler temperatures.
Great
Dwarf Shrimp
Neocaridina davidi
Weather Loaches are active foragers with large mouths and will likely consume small shrimp and fry.
Compatible with caution
Discus
Symphysodon aequifasciatus
Discus require much higher tropical temperatures that are unsuitable for Weather Loaches, and would be stressed by the loach's hyperactive behaviour.
Not recommended
Oscar
Astronotus ocellatus
Large, aggressive tropical cichlids will attack and likely consume the loaches, and require incompatible temperatures.
Not recommended

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