Eurasian Minnow (Common Minnow)

Habitat and Natural Environment

The Eurasian Minnow (Phoxinus phoxinus), often called the Common Minnow, is a small cyprinid native across much of Europe and parts of northern Asia. It naturally inhabits cool, well-oxygenated freshwater—typically headwaters, streams, small rivers, and the margins of clear lakes—often over gravel, pebble, and sand substrates.

In the wild it is commonly found in areas with steady flow and high dissolved oxygen, using submerged vegetation, roots, and stones for cover. Seasonal temperature swings are normal in its native range; the species is adapted to cooler conditions compared with most tropical aquarium fish.

Tank Setup Requirements

Tank Size and Grouping

Eurasian Minnows are active schooling fish that do best in groups. A larger footprint matters more than height because they spend most of their time cruising midwater and along current seams.

• Recommended group: 8–12+ individuals (larger shoals show more natural behavior and better coloration)
• Minimum practical tank: ~75 L / 20 gal long for a small group; 110+ L / 30+ gal long is preferable
• Cover: a tight-fitting lid is recommended; they can startle and jump, especially in high-flow tanks

Water Parameters and Filtration

Aim for cool, clean, oxygen-rich water with moderate to strong filtration. Stability and oxygenation are more important than chasing an exact pH number.

• Temperature: ~10–18°C (50–64°F) typical; short seasonal variation is tolerated if changes are gradual
• pH: ~6.5–8.0 (neutral to slightly alkaline is commonly fine)
• Hardness: soft to moderately hard is acceptable
• Flow/oxygen: moderate flow with strong surface agitation; use a quality filter and consider a powerhead or air stone
• Maintenance: frequent partial water changes to keep nitrate low; minnows respond poorly to chronically degraded water quality

Aquascape and Decor

Replicate a stream-like environment with open swimming space and broken lines of sight. A mix of smooth gravel/pebbles, rounded stones, driftwood, and hardy plants provides cover without restricting movement.

• Substrate: sand to fine gravel; add rounded pebbles/cobbles for a natural look
• Hardscape: river stones, wood, and root-like structures to create eddies and resting zones
• Plants: cool-tolerant species (e.g., hornwort, waterweed/Elodea, Vallisneria in cooler setups) or mosses attached to stones/wood
• Lighting: moderate; provide shaded areas with plants/wood to reduce skittishness

Feeding and Diet

Eurasian Minnows are omnivorous micro-predators that feed on small aquatic invertebrates, insect larvae, zooplankton, and plant matter/detritus. In captivity they thrive on a varied diet with a strong emphasis on small, protein-rich foods.

• Staples: high-quality small pellets or micro granules; quality flakes can work but are less ideal as a sole diet
• Frozen/live: daphnia, cyclops, artemia (adult or baby depending on fish size), bloodworms (as an occasional treat), chopped blackworms
• Occasional plant matter: spirulina-based foods or finely blanched vegetables in small amounts
• Feeding frequency: 1–2 small feedings daily; remove excess to protect water quality

Behavior and Temperament

Common Minnows are peaceful, lively schoolers that spend much of the day actively cruising in midwater. In proper groups they are confident and display subtle social interactions; in small numbers they can become shy and prone to stress.

• Temperament: generally peaceful; may compete for food vigorously but rarely causes damage
• Social needs: must be kept in a shoal; larger groups reduce fin nipping and skittishness
• Activity level: high; appreciates current and ample swimming room
• Compatibility: best with other cool-water, non-aggressive species that tolerate similar flow and temperature

Breeding (if applicable)

Eurasian Minnows are egg scatterers and can be bred in captivity, but success is more likely in a dedicated setup that mimics seasonal cues. In nature, spawning is often triggered by rising temperatures and longer day length in spring, with fish depositing adhesive eggs over gravel, plants, or spawning mops.

Breeding Setup and Conditioning

• Condition adults with abundant live/frozen foods (daphnia, artemia, etc.)
• Provide a separate breeding tank with clean, cool water and strong aeration
• Use fine-leaved plants, spawning mops, or a bed of clean gravel/pebbles to receive eggs
• Introduce a gentle seasonal change: gradually increase temperature and photoperiod to simulate spring

Egg and Fry Care

• After spawning, remove adults or move eggs to prevent predation (adults may eat eggs and fry)
• Keep water pristine and well-oxygenated; mild antifungal measures may be needed in some setups
• First foods: infusoria, rotifers, or commercial fry foods; then graduate to baby brine shrimp and microworms as fry grow
• Provide gentle filtration (sponge filter) to protect fry

Health and Common Issues

When kept cool with high oxygen and excellent water quality, Eurasian Minnows are generally hardy. Most problems in captivity come from chronic warmth, insufficient oxygenation, crowding, and poor quarantine practices.

• Low oxygen stress: rapid gill movement, hanging near the surface/outflow; improve aeration, reduce temperature, and check stocking/flow
• Heat stress: lethargy, poor appetite, increased disease incidence; move to cooler conditions and ensure strong surface agitation
• External parasites/Ich: flashing, white spots; quarantine new fish, treat appropriately, and avoid temperature-based “treatments” that require warming beyond safe ranges
• Fin damage: usually from cramped conditions or too-small groups causing social stress; increase shoal size and tank length
• Water quality issues: sensitivity to ammonia/nitrite; ensure cycled filtration and maintain regular water changes