Blue loach - Yasuhikotakia modesta

Scientific name: Yasuhikotakia modesta

Common name: Blue loach

Family: Cobitidae

Usual size in fish tanks: 20 - 24 cm (7.87 - 9.45 inch)

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Recommended pH range: 6.5 - 8

Recommended water hardness: 5 - 12°N (89.29 - 214.29ppm)

0°C 32°F30°C 86°F

Recommended temperature range: 24 - 27 °C (75.2 - 80.6°F)

The way how these fish reproduce: Spawning

Where the species comes from: Southeast Asia

Temperament to its own species: peaceful

Temperament toward other fish species: peaceful

Usual place in the tank: Bottom levels

General Information

The Blue Loach (also sold as Redtail/Red-finned Botia), scientific name Yasuhikotakia modesta (syn. Botia modesta), is a robust river loach native to mainland Southeast Asia. Wild populations occur in the Mekong, Chao Phraya, and Mae Khlong basins (Thailand, Laos, Cambodia, Vietnam). In nature it inhabits large, often turbid rivers with muddy bottoms and migrates seasonally with the flood pulse. Typical adult size in aquaria is 18–22 cm (7–9″); wild maxima approach ~25 cm SL.

Food and Feeding

A largely nocturnal benthic omnivore with a strong preference for invertebrates. Offer sinking pellets/tablets as the staple and rotate live or frozen foods (bloodworms, blackworms, chopped earthworms, daphnia, insect larvae, brine shrimp). Feed after lights-out or under dim light so slower fish get their share. Avoid mammalian/avian meats (e.g., beef heart) as routine diet.

Sexing

No reliable colour/fin differences; mature females are typically fuller-bodied than males when gravid.

Breeding

Home-aquarium breeding is not documented. In the wild the species is strongly migratory, moving into tributaries to spawn during the early flood season, then returning to main channels as waters recede—conditions that are difficult to replicate indoors. Commercial production (where available) is generally via hormones.

Lifespan

Expect many years with good care; reports of 8 years exist, and double-digit lifespans are plausible with excellent water quality and diet.

Tank Requirements & Water Parameters

Tank size & footprint: large bottom area is key. For a group, plan ≥120–150 cm (4–5′) length with robust filtration and high oxygenation.
Water: pH ~6.5–8.0; hardness ~5–12°dH (tolerant a bit beyond); temperature ~24–27 °C (75–81 °F). Keep parameters stable.
Décor & flow: sand or smooth fine gravel, wood/rock piles and tubes for retreats, and moderate current to mimic rivers. Dim/subdued lighting is appreciated.
Maintenance: weekly 25–40% water changes; secure lid (adept at squeezing through gaps).

Compatibility & Tank Mates

Semi-aggressive/boisterous. Best kept in a group of 5 conspecifics to diffuse intraspecific sparring (loach hierarchy), provided the tank is large and structured. Avoid very small fish and delicate long-finned species; choose similarly robust midwater companions.

Behaviour & Usual Place in the Tank

Bottom levels (demersal): rests in caves by day, becomes active from dusk through night, foraging along the substrate and among structures. In river setups it enjoys cruising in the boundary layer near the bottom.

Short Description

Blue Loach / Redtail Botia (Yasuhikotakia modesta) is a large Southeast Asian river loach. Provide a big, well-oxygenated, covered tank with sand and numerous hides, feed sinking meaty foods after dark, and keep in a proper group to spread dominance behaviour. Breeding in home aquaria is unreported.

Q&A

South Asia or Southeast Asia? Southeast Asia (Mekong/Chao Phraya/Mae Khlong basins), not the Indian subcontinent.
How big do they get? Commonly 18–22 cm in aquaria; FishBase lists a maximum of 25 cm SL.
Can they be sexed visually? Not reliably—females are just fuller when gravid.
Do they breed in tanks? Not naturally; it’s a migratory spawner tied to flood cycles.