Eurasian Minnow

Geographic Origin and Biotope: One of the most widespread Eurasian freshwater fish, from Pyrenean torrents to Siberia. Inhabits crystal-clear, fast-flowing streams with pebble and gravel beds in permanently cold (5-15°C), oxygen-saturated water.

Taxonomy and Morphology: Tiny cyprinid (max 8-10 cm), fusiform and hydrodynamic. Microscopic deeply embedded scales give a nearly smooth appearance. Small terminal mouth without barbels.

Social Behavior: Obligate schooler in groups of dozens or hundreds. Needs 10-15+ in aquariums. Alone, it hides terrified and refuses food.

Coloration and Sexual Dimorphism: Mostly anonymous gray-olive. But in spring, males undergo a stunning transformation: fiery crimson-red belly, iridescent green-black back, and white keratinized nuptial tubercles on the lips. One of the most underrated chromatic spectacles in ichthyology.

Tank Setup: Long aquarium (min 100 cm) with strong current from powerheads. Pebble and fine gravel substrate. Only cold-water plants (Fontinalis). Unheated, ideally in a cool room or basement.

Feeding: Cold-water omnivore. Accepts flakes, pellets, frozen bloodworms, daphnia. Not demanding but needs variety to stimulate breeding colors.

Water Quality: CRITICAL: temperature 5-18°C ideal, absolute maximum 20-22°C briefly. Above 22°C it gasps and dies of cardiac failure and hypoxia within weeks. Maximum oxygenation mandatory. pH 6.5-8.0.

Compatibility: Only with cold-water fish: White Clouds, Bitterlings, Sunbleaks, Hillstream Loaches. Incompatible with ANY tropical fish.

Reproduction: Stimulated by seasonal simulation: winter at 5-8°C followed by spring warming to 12-16°C. Eggs scattered on clean gravel in current. No parental care.

Risks: Heat is the absolute killer. Ich is the most common disease, favored by summer thermal stress. Summer heat waves in outdoor tanks cause mass mortality. Supplemental aeration in summer is a survival obligation.