Quick Stats
| Adult Size | 15–25 cm |
| Minimum Tank | 30 gal |
| Temperature | 15–24°C (unheated) |
| pH Range | 6.5–8.0 |
| Hardness (GH) | 5–25 dGH |
| Difficulty | Easy |
| Temperament | Peaceful, social |
| Diet | Omnivore — sinking pellets, frozen bloodworms, brine shrimp, blanched vegetables |
| Schooling | 3+ recommended |
Tank Setup
Weather loaches (Misgurnus anguillicaudatus, also called Dojo Loaches) are native to East Asia and adapted to a huge temperature range — they survive from 5°C to 30°C, making them one of the hardiest aquarium fish available. A 30 gallon tank is the minimum for a group of three. They are active swimmers that use the entire bottom of the tank.
Water parameters: temperature 15–24°C (unheated in a normal house is ideal), pH 6.5–8.0, hardness 5–25 dGH. They are unfussy about water chemistry as long as it's stable and clean. Strong filtration matters — they produce significant waste for a bottom-dweller.
Substrate is the most important setup decision. Weather loaches burrow constantly — sand is essential, gravel damages their delicate skin and barbels. Provide 5+ cm of smooth play sand. They also need a tight-fitting lid with no gaps — weather loaches are notorious escape artists and will find any opening. The lid must be weighted or clipped; they can push loose-fitting glass aside.
Tank Mates
Weather loaches are peaceful, social, and completely non-aggressive. They are best kept in groups of three or more — a single weather loach will hide constantly and pine. They interact with each other by piling on top of one another in a way that looks alarming but is normal social behaviour.
Compatible tank mates: Fancy Goldfish (perfect cold-water overlap), White Cloud Mountain Minnows, Zebra Danios (at the cool end of their range), and other cold-water species. They coexist well with all shrimp large enough not to be eaten (Amano shrimp, adult Cherry Shrimp) and Japanese Trapdoor Snails.
Avoid: tropical species that need 24°C+ (the loach will tolerate it but it shortens their lifespan), aggressive bottom-dwellers (cichlids, large catfish), and small fish that could be eaten at night when the loach is most active. Also avoid housing with Chinese Hillstream Loaches — they compete for the same niche.
Diet & Feeding
Weather loaches are omnivores with a strong preference for meaty foods. They eat sinking pellets, frozen bloodworms, frozen brine shrimp, tubifex worms, and the occasional blanched vegetable. They forage constantly in the substrate, eating leftover food that other fish miss — useful cleanup behaviour.
Feed once or twice daily. They are most active at dusk and dawn, so an evening feeding of frozen food is appreciated. Sinking pellets ensure they get their share — surface-feeding fish will eat floating food before it reaches the bottom.
Weather loaches will eat small shrimp and snails if they catch them. They cannot crush snail shells (no teeth), but they will eat snails that have died or that they can swallow whole. Pest snail populations stay in check but are not eliminated by weather loaches.
Common Health Issues
Weather loaches are extremely hardy. The main health issue is damage from gravel substrate ( barbels erode, skin scrapes get infected) — fix with sand. They are also prone to jumping injuries when startled, which is why a tight lid matters.
They breathe atmospheric air using a modified intestine as an accessory breathing organ — you will see them surface, gulp air, and swim back down. This is normal, not a sign of poor water quality. The air passes through their digestive system and they extract oxygen from it.
Lifespan is 10+ years in good conditions. The 'weather' behaviour — increased activity and surface-gulping before storms — is caused by falling barometric pressure, which they detect via their swim bladder. It's not a superstition; it's a real barometric response.
Breeding
Breeding weather loaches in the home aquarium is rare but documented. They are seasonal spawners, triggered by a temperature rise in spring (from 15°C to 20–22°C) combined with a large water change using slightly cooler water.
Sexing: females are larger and rounder, especially when full of eggs. Males develop small breeding tubercles on the pectoral fins. To attempt breeding, condition a group of 4–6 adults with high-protein frozen foods for 2 weeks, then trigger with a 50% cool water change.
Spawning is boisterous — the males chase the females through plants, scattering thousands of adhesive eggs. Eggs hatch in 3–5 days. Remove adults immediately (they eat eggs). Feed fry infusoria for the first week, then microworms and baby brine shrimp. Most home breeding happens in outdoor ponds rather than indoor tanks.
Frequently Asked Questions
Why is my Weather Loach going crazy?
Weather loaches become agitated and surface-gulp when barometric pressure drops — usually before a storm. This is the behaviour that earned them the name 'weather fish'. It's not a sign of poor water quality; it's a real barometric response. If your loach is constantly frantic, however, check ammonia and nitrite levels.
Do Weather Loaches need a heater?
No — they are cold-water fish that prefer 15–24°C. An unheated tank in a normal house is ideal. They can survive extreme temperatures (5–30°C) but thrive in the cool room-temperature range.
Do Weather Loaches need sand?
Yes — sand is non-negotiable. They burrow constantly and gravel damages their barbels and skin. Use 5+ cm of smooth play sand. Avoid sharp gravels and crushed coral.
Can Weather Loaches live with goldfish?
Yes — they are one of the best tank mates for fancy goldfish. Both species prefer cold water (15–22°C), both are peaceful, and the loach cleans up leftover food the goldfish miss. Ensure the tank is 30+ gallons and has a tight-fitting lid (weather loaches escape).