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Belica

Leucaspius delineatus

The Sunbleak is a small schooling fish found in slow European freshwater ponds. It needs a spacious aquarium with dense margin planting to mimic its natural habitat, along with ample open swimming space.

Taxonomy

Class:Actinopteri

Order:Cypriniformes

Family:Cyprinidae

Genus:Leucaspius

Species:Leucaspius delineatus

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Water Temperature

10 - 20 °C

pH Value

6.5 - 8

Water type

Freshwater

Tank level

Surface and middle

Adult size

9 cm

Minimum tank volume

100 L

Minimum group

>= 1

10 - 20 dGH

5 - 10 dKH

TDS

200 - 400 ppm

Conductivity

313 - 625 uS/cm

Species description

Geographical Origin and Habitat: Leucaspius delineatus, commonly known as the belica, moderlieschen, or sunbleak, is widely distributed across Central and Eastern Europe, extending eastwards into Western Asia. It primarily inhabits stagnant or slow-flowing freshwater bodies, including ponds, oxbow lakes, swamps, drainage ditches, and shallow lakes with dense aquatic vegetation. It is highly adaptable to low-oxygen environments and prefers shallow, shaded shoreline areas under overhanging reeds.

Taxonomy and Morphology: It belongs to the Cyprinidae family, genus Leucaspius, of which it is the only recognized species. It is a small cyprinid fish, reaching a maximum total length of 6 to 9 centimeters. Its body is slender, moderately compressed laterally, with an incomplete lateral line that extends across only the first 2 to 12 scales. Its upturned mouth is a specific evolutionary adaptation for feeding directly from the water surface.

Social Behavior: This is a highly gregarious, peaceful schooling species that must be kept in groups of at least 8 to 10 individuals to feel secure. It swims primarily in the upper and middle layers of the water column. In a school, it maintains a tight structure to deter predators; when isolated or kept in insufficient numbers, it becomes extremely shy, stressed, and is prone to jumping.

Coloration and Sexual Dimorphism: The body coloration features a greenish or brownish-olive back that fades into bright, reflective silvery sides with bluish metallic highlights. A distinct iridescent blue or violet longitudinal stripe is visible along the sides, especially toward the tail. The fins are transparent or slightly greyish. Sexual dimorphism is subtle: mature females are rounder, and males develop small nuptial tubercles on their heads during the breeding season.

Care, breeding and tankmates

Aquarium Setup: Requires an aquarium of at least 100 liters (approx. 25 gallons) to house a small school. The setup must include dense margin and background planting (using species like Ceratophyllum demersum or Vallisneria) to mimic its natural pond habitat and provide security. Ample open swimming space must be left in the center. A tight-fitting lid is mandatory, as they are agile jumpers. A sandy or dark fine gravel substrate is ideal.

Diet and Feeding: An omnivorous species that feeds primarily at the surface. In captivity, it readily accepts high-quality floating flakes or micro-granules. To encourage natural behaviors and prepare them for breeding, supplement their diet with live or frozen foods of appropriate size, such as daphnia, cyclops, brine shrimp, mosquito larvae, and small insects like fruit flies.

Water Quality: Being a temperate coldwater species, it prefers temperatures between 10 and 22°C, though it can tolerate temporary summer peaks up to 25°C. Water pH should be maintained between 6.5 and 7.8, with hardness ranging from soft to moderately hard (8-18 dGH). Efficient mechanical and biological filtration is necessary, but water flow should be kept gentle to mimic its native calm waters.

Compatibility and Cohabitation: Extremely peaceful, making it a perfect resident for temperate community aquariums or European native biotope setups. It coexists well with other peaceful coldwater species such as Rhodeus amarus (bitterling), Gasterosteus aculeatus (stickleback), or small loaches. Avoid housing with large predatory fish (such as perch or pike) or tropical fish that require high constant temperatures.

Aquarium Breeding: Breeding in captivity is relatively simple. They lay adhesive eggs arranged in ribbons or rings wrapped around plant stems or the undersides of leaves. The male cleans the spawning site and guards the eggs, fanning them with his fins until they hatch in a few days. Once hatched, the fry should be fed with infusoria and rotifers, followed by newly hatched brine shrimp.

Risks and Diseases: While robust, they suffer from weakened immune systems if kept constantly in warm water above 24-25°C, making them susceptible to fungal and bacterial infections. They can contract ich (white spot disease) if exposed to sudden temperature drops. Adequate filtration and regular partial water changes are key to prevention.

Geographic Origin and Distribution

Leucaspius delineatus, commonly known as the belica, moderlieschen, or sunbleak, is widely distributed across Central and Eastern Europe, extending eastwards into Western Asia. It primarily inhabits stagnant or slow-flowing freshwater bodies, including ponds, oxbow lakes, swamps, drainage ditches, and shallow lakes with dense aquatic vegetation. It is highly adaptable to low-oxygen environments and prefers shallow, shaded shoreline areas under overhanging reeds.

Origin

Europe, Mediterranean, and West Asia

Fish profile

Temperament: Semi-aggressive
Diet: Omnivore
Sex ratio: School
Feeding frequency: Twice daily
Bioload: Leucaspius delineatus produces a very low bioload. They are small and relatively clean fish. Standard filtration is perfectly sufficient.
Flow: Stagnant
Reproduction: Oviparous
Compatibility & tankmates: This is a highly peaceful schooling fish. Keep them with other small, gentle species. Avoid any large or predatory tank mates.
Tank level: Top/Middle

FishBase

Window to the official scientific data of the species

Data synced on: 06/15/2026

Scientific Parameters & Models

Trophic level: 3.2 ± 0.4 se
Resilience: Medium (1.4 - 4.4 years)
Generation time: 4.4 years
Phylogenetic uniqueness (PD50): 1
Bayesian Length-Weight: a = 0.00724, b = 3.13

Image gallery

Licensed images linked to the species or, when marked, to the closest representative taxon.

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Recommendations grouped by close relatives, companion choices, and similar care.

Variants and close relatives

Same atlas type, nearby scientific identity, genus, or family.

Rosy Bitterling

Rhodeus ocellatus

Species description

Care, breeding and tankmates

Geographic Origin and Distribution

Origin

Fish profile

Scientific Parameters & Models

Image gallery

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