Family: Cyprinidae
A peaceful carnivore cyprinidae from China, the Korean Peninsula, Russia — moderate care.
Opsariichthys bidens is a Cyprinidae. In the aquarium it stays semi-aggressive. Plan on 18.3–26.1 cm of adult fish at 10–20 °C. Related profiles: Opsariichthys pachycephalus, Opsariichthys evolans, Opsariichthys hainanensis.
Yes, if they are small enough. Hooksnout carp are honest predators. House them with fish too large to swallow and fast enough not to be harassed.
Yes — a small group of similarly sized individuals works and reduces pacing. Males may spar in breeding condition, but serious damage is uncommon in roomy, cool tanks.
Only beginners prepared for a large, cool, high-flow setup with heavy filtration. The fish itself is hardy; the tank it needs is the commitment.
Quickly on adequate feeding: purchased at 10 cm, expect near-adult size within a year, after which growth slows while girth continues.
Intermediate — the 'stream-type' pick among Chinese natives. Base parameters aren't harsh (10–20 °C eurythermal, pH 6.5–7.5 tolerant), but it's a creek fish: high oxygen and strong current are hard requirements. Kept in a small, still tank it slowly wastes away. Scaped correctly, it's the stream tank's beauty lead: breeding males flash orange-red with blue-green iridescence, top-tier among natives.
The name comes from its gape: large mouth with a notch in the jaws that opens like a horse's muzzle — a tool for snatching surface prey. The epithet bidens means 'two-toothed', referencing the two prominent premaxillary teeth. It's the 'standard fish' of Chinese streams, found in hill creeks from the northeast to the far south.
261 L is the floor; 300–400 L+ in practice. It swims at high speed with strong bursts and repeatedly injures itself against glass in small tanks. Scape is standard creek-tank: cobblestone, fine sand, strong current (point the filter output or add a circulation pump), and high oxygen (air stone or agitated outflow). Without strong flow, both color and condition suffer.
Eurythermal, cool-leaning — 10–20 °C is the comfort zone, no heater needed, with summer cooling and aeration above 26 °C. What it truly fears is temperature swing: a 2 °C gap on change water can trigger stress. Winter appetite loss is normal rhythm — don't force-feed with heat. Water chemistry is undemanding, but oxygen must be ample — the iron rule of creek fish.
Carnivore-leaning: aquatic insects, small fish and shrimp, fallen surface insects. Captive acceptance is decent: frozen bloodworms, shrimp meat, fish chunks, sinking carnivore pellets once trained. Its hunting style is pursuit — it bursts after prey — so tease-feeding (wiggling food with tweezers) triggers the instinct and maximizes the display.
Breeding-season male territory behavior. Marriage color and aggression surge together: males claim patches of ground and evict rival males — including bigger ones. Mixing advice: groups of six or more are fine outside breeding (diffusing individual conflict); during breeding either isolate males or provide very large water (800 L+) so the loser can flee. Fights aren't lethal (nothing like snakeheads), but chronic suppression drains condition.