Blue Line Venus Minnow (Aphyocpris cf. lini)

Common Name

Blue Line Minnow
Aphyocypris cf. lini

In the aquarium trade, this fish is often sold as Aphyocypris cf. lini and nicknamed Blue Line for its narrow, metallic stripe. The cf. tag is used when an import resembles a known species, in this case Aphyocypris lini, but a firm scientific identification is not certain from trade sources alone.

Origin and Habitat

Aphyocypris lini is a small minnow native to southern China and was historically recorded from Hong Kong, with later records and related reports from nearby parts of southeast China. Aquarium fish sold as Blue Line are generally attributed to the same broader region, although exact collection localities are rarely disclosed.

In the wild, Aphyocypris lini is associated with clear, shallow ditches, rivulets, and small streams where dense aquatic vegetation is present. These habitats are typically slow moving to gently flowing, with sandy or fine gravel areas and plenty of plant growth that provides shelter and feeding surfaces.

Biotope notes. A realistic biotope style aquarium can be built around a shallow, plant rich lowland stream or ditch. Focus on dense submerged vegetation or fine leaved plants, marginal cover, and open swimming lanes. In the same southern China and Hong Kong lowland waters, other regionally associated native freshwater fishes reported include small cyprinids such as Tanichthys albonubes and various stream cyprinids, along with other small, peaceful species that use vegetated margins.

Temperature and Water Conditions

A good long term aquarium range is 18 to 24 °C, about 64 to 75 °F, with steady temperature and strong oxygenation. Wild water chemistry reported for Aphyocypris lini is alkaline, with pH around 7.5 to 7.8 in compiled databases.

We do not recommend chasing or altering water parameters except in special breeding situations. Stable conditions are far more important.

This group is best kept in clean, well filtered water with zero ammonia and nitrite and low nitrate. Moderate to hard water is generally suitable for fish attributed to Aphyocypris lini, and stable mineral content tends to support consistent appetite and coloration.

Appearance and Size

Blue Line Aphyocypris are slender, torpedo shaped minnows with a bright lateral accent that flashes as they turn. Depending on the individual and light angle, the stripe can read as silver, green blue, or gold, with a translucent body and clear fins.

Sexual differences are subtle. Males may show slightly stronger sheen and a slimmer profile, while females can appear a bit deeper bodied when full of eggs.

Maximum size reported for Aphyocypris lini is about 5 cm, roughly 2.0 inches total length.

Diet in the Wild

Wild diet information for Aphyocypris lini is limited in the aquarium literature. Based on its habitat and behavior, and on documented use of Aphyocypris minnows as larval mosquito predators, this group is best understood as an opportunistic micro predator and picker that feeds on small aquatic invertebrates, insect larvae, and tiny crustaceans, with some grazing on biofilm and attached micro foods in vegetated areas.

Feeding in Captivity

Offer small, fast to eat foods that match their tiny mouth size. A practical rotation is a quality micro pellet or fine flake as the daily staple, plus frozen foods such as cyclops, baby brine shrimp, and finely chopped daphnia several times per week.

Feed one to two small meals per day, only what the group finishes quickly. Occasional live foods, especially baby brine shrimp or small daphnia, are excellent for conditioning and can intensify the metallic line when combined with a varied diet and clean water.

Behavior and Tank Setup

This is a peaceful schooling fish that does best in a group. In small numbers they can become timid, but in a proper school they stay active and show better color.

For a display group, a minimum of about 40 liters, roughly 10 gallons, works for 8 to 12 fish, but more space is always better. For larger groups or mixed community setups, 75 liters, about 20 gallons, provides a calmer, more natural swimming pattern.

Build the aquascape with dense plant cover and a few open lanes. Use gentle to moderate flow, fine filtration that does not pull in tiny fish, and good surface agitation for oxygen. A secure lid is recommended because small minnows can jump when startled.

Choose equally peaceful tank mates such as small rasboras, ricefish, and calm hillstream friendly species that do not outcompete them at feeding time. Avoid fin nippers and larger predatory fish. Fry and very small shrimp may be eaten if they fit in the mouth.

Breeding

In the aquarium, fish attributed to Aphyocypris lini are expected to be egg scatterers that spawn in vegetation. Adults may eat eggs and fry, so a dedicated breeding setup or protective spawning media improves success.

Use cool to mild temperatures, very clean water, and frequent small feedings of live or frozen foods to condition adults. Provide fine leaved plants, spawning mops, or dense moss where eggs can fall and remain protected.

Breeder’s Tips

• Condition with small live foods, especially baby brine shrimp and daphnia
• Use a dense spawning mop or fine leaf plants so eggs can drop out of reach
• Remove adults after spawning, or use a mesh divider to protect eggs
• Start fry on infusoria and very small powdered foods, then baby brine shrimp once they can take it
• Do small, frequent water changes to keep growth steady and avoid bacterial blooms

Quick Facts

• Scientific name: Aphyocypris cf. lini
• Common name: Blue Line Minnow
• Origin: Southern China, including the Hong Kong region and nearby southeast China records for Aphyocypris lini
• Adult size: Up to about 5 cm, about 2.0 inches
• Temperature: 18 to 24 °C, about 64 to 75 °F
• pH: About 7.5 to 7.8 reported in compiled references, keep stable rather than exact
• Hardness: Moderate to hard water is generally suitable
• Temperament: Peaceful schooling fish
• Diet: Small invertebrates and insect larvae, plus biofilm and micro foods
• Breeding: Egg scatterer, use plants or spawning mops and protect eggs

Tropical Fish Co. Notes

Blue Line Aphyocypris are a great fit for planted nano tanks where you want constant motion without aggression. Their best look comes from a large enough group, strong plant cover, and clean, well oxygenated water. We like them with other calm, small fish that share similar flow and temperature needs, and we avoid fast, pushy feeders that keep them pinned to the corners.

Because the cf. identification indicates uncertainty, we treat this fish like a small subtropical Aphyocypris minnow. If you keep them on the cooler side with stable parameters and a varied micro diet, they tend to reward you with better color, tighter schooling, and strong appetite.