Aquarium ~280L+ / 75gal+ with a 4ft+ (120cm) footprint for a trio (6ft better); ponds suit them
Social needs
Social - keep 3+ together (5+ better)
Diet
Omnivore (bottom-feeder, sinking foods)
Time
Moderate (daily feed, weekly water changes)
Cost
Medium (cheap fish, large tank)
Overview
The Dojo Loach, also sold as the weather or pond loach, is a thick-bodied, eel-shaped East Asian loach that comes in a mottled brown wild form and a popular golden morph.
Its defining party trick is weather-sensing: a drop in barometric pressure before a storm sends the whole group darting and spiralling around the tank, which earned it the weatherfish name.
Unlike the site's other loach, the small and secretive Kuhli, the Dojo is a bold, out-in-the-open fish that commonly reaches 15-25 cm (6-10 in) and can top 30 cm (12 in), and it actively interacts with its keeper, often learning to feed from the hand.
Its intermediate rating reflects the space a full-grown group needs and its temperate-water requirements, not any fragility.
One serious caveat comes before purchase: this species is highly invasive when released, and keeping it is prohibited or restricted in several US states (Michigan, Minnesota, and Oregon among them) and other countries.
Check your local laws before buying, and never release an unwanted fish into any waterway.
Housing
Dojo Loaches are temperate fish, not tropical, and do best at 15-23C (59-73F) in an unheated tank in a normal room, with the mid-60s F being the sweet spot for active behaviour and longevity.
Sustained temperatures above about 25C (77F) raise their metabolism, stress their immune system, and measurably shorten their lives, which is the most common way keepers get this species wrong.
A group of three adults needs at least about 280 litres (75 gallons) with a 4ft-plus (120cm) footprint, and a 6ft tank better suits a full-grown group, because these are large, active, substrate-length fish that swim hard when the pressure drops.
Provide several centimetres of soft sand so they can bury themselves with just the head showing, which is natural resting behaviour and impossible on gravel.
They are intestinal breathers that gulp air at the surface, and they are legendary escape artists that climb airline tubing and squeeze past filter cut-outs.
A tightly fitted, weighted lid with every gap sealed is non-negotiable, and the tank must be fully cycled with pH 6.5-8.0 and weekly 30% water changes.
Diet
Dojo Loaches are greedy bottom-feeding omnivores that take almost anything reaching the substrate.
Feed sinking pellets and wafers as the staple, plus frozen or live bloodworm, blackworm, and brine shrimp, and occasional blanched vegetables such as cucumber and courgette.
They will happily eat small aquarium snails, which makes them useful in snail-plagued temperate tanks.
Many settle in well enough to wriggle up and take food directly from their keeper's fingers.
Their appetite is their weakness, and an unmeasured feeder will produce an obese loach in months.
Offer only what the group clears in a few minutes once or twice daily, and make sure food actually reaches them if faster surface-feeders like goldfish share the tank.
Health
Dojo Loaches are hardy in cool, clean water, and most health problems trace back to being kept too warm or in an immature tank.
Like other loaches they have tiny embedded scales and a sensitive slime coat, so salt, copper, and full-strength medications must be avoided or dosed at reduced strength.
Red blotch disease, showing as inflamed red patches on the belly and flanks, is strongly associated with this species when it is kept warm or in poor water, and it needs prompt cooling, pristine water, and veterinary-guided antibacterial treatment.
Newly imported, farm-raised stock frequently carries internal parasites, so quarantine new fish for 4 weeks and watch for a fish that eats well yet stays thin.
Their intestinal breathing lets an escapee survive on the floor for a surprisingly long time, but many are still lost this way.
Check the lid after every feed, and return any found jumper to the tank promptly, as it may well recover.
Temperament
Dojo Loaches are peaceful, tactile, and genuinely social, resting in piles and following each other around the tank.
Keep at least three together, and ideally five or more, because a solitary Dojo becomes listless and hides far more.
They are among the most interactive freshwater fish, approaching the glass when their keeper appears and often tolerating a gentle touch at feeding time, which is why keepers call them the puppies of the fish world.
This boldness makes them a daytime centrepiece rather than a fish you glimpse after lights-out.
Match them only with other temperate species, with goldfish, White Cloud Mountain Minnows, and Zebra Danios being the classic companions.
They ignore tankmates they cannot swallow, but dwarf shrimp and very small fish may disappear overnight, and tropical communities are the wrong home for temperature reasons alone.
A good fit for
Unheated, temperate aquariums and coldwater ponds
Companions for goldfish, White Clouds, and other coldwater fish
Keepers wanting an interactive, hand-tame fish
Soft sand-bottom tanks with a 4ft-plus footprint
Snail control in coldwater tanks
Common mistakes to avoid
Sustained warmth over ~25C (77F) shortens their lives
Intermediate
Intermediate
Intermediate
Intermediate
Intermediate
Intermediate