Species description

Care, breeding and tankmates

Fish profile

Temperament

Semi-aggressive

Boraras naevus is an extremely peaceful and somewhat timid species that exhibits classic schooling behavior. Because of their tiny size, they are easily intimidated by larger or more boisterous tank mates. They spend their days swimming together in a coordinated fashion, which helps build their confidence. Males may occasionally display mock battles or territorial behavior when breeding, but these interactions are entirely peaceful and harmless.

Diet

Omnivore

In their natural habitat, Boraras naevus are micropredators feeding on tiny insects, zooplankton, and small worms. In an aquarium, their diet must reflect their small mouth size, requiring crushed flakes, micro-granules, or powdered foods. Providing regular meals of live and frozen items, such as baby brine shrimp or Daphnia, is highly recommended to maintain their health. A varied and high-quality diet is the key to bringing out their most intense red coloration.

Life expectancy

3-5 years

In captivity, Boraras naevus typically has a lifespan of three to five years when kept under optimal conditions. Their longevity is closely linked to water stability and the quality of their overall care. A stress-free environment, blackwater conditions, and a nutritious diet will significantly help them reach their maximum age. In poorly maintained tanks or under constant stress, their lifespan can be drastically shortened.

Sex ratio

Group

When stocking Boraras naevus, they should always be kept in mixed-sex groups of at least eight to ten individuals. In a proper school, the sex ratio naturally balances out, which reduces overall stress and shyness. Having multiple males in the group is highly beneficial, as it encourages them to display their best red coloration and perform harmless sparring behaviors. Keeping too few specimens or an unbalanced group can result in timid fish that remain hidden.

Feeding frequency

Twice daily

Due to their high metabolism and small stomach capacity, Boraras naevus should be fed two to three times daily. Offering small portions that they can consume within a minute or two helps prevent overfeeding and water pollution. Feeding them multiple times a day also ensures that the sub-dominant individuals receive adequate nutrition. It is beneficial to schedule a fast day once a week to help clear their digestive systems.

Bioload

Low

Due to their miniature size, Boraras naevus has an exceptionally low bioload. They produce very little waste, making them excellent candidates for small nano aquariums. However, because they are highly sensitive to fluctuating water parameters and built-up nitrates, they still require consistent, gentle filtration. A stable ecosystem with regular, small water changes is crucial to keep their environment clean and ensure their health.

Flow

Stagnant

Boraras naevus naturally inhabits slow-moving swampy areas and stagnant blackwater environments in the wild. Consequently, they have a strong preference for weak water flow in the aquarium. Strong currents will stress these tiny fish, forcing them to exhaust themselves by constantly fighting the water movement. A gentle sponge filter or an adjustable filter with a spray bar is ideal to keep the current minimal.

Jump risk

Yes

There is a moderate to high risk of Boraras naevus jumping out of the aquarium, particularly when they are startled or introduced to a new environment. Because they swim in the upper water levels, any sudden movement near the tank can cause them to leap. To prevent tragic losses, a tight-fitting lid or cover slides are absolutely essential. Additionally, incorporating floating vegetation can help cover the water surface and reduce their urge to jump.

Reproduction

Oviparous

Breeding Boraras naevus is relatively easy but requires a dedicated setup for high success rates. They are continuous egg scatterers that lay small batches of eggs daily among fine-leaved plants like mosses. They exhibit no parental care and will eagerly consume their own eggs if given the chance. To raise the fry, adults must be removed, and the tiny hatchlings should be fed micro-foods such as infusoria and paramecium.

Compatibility & tankmates

Because of their minuscule size, Boraras naevus is only compatible with small, peaceful tank mates. Excellent companions include dwarf freshwater shrimp, dwarf Corydoras, Otocinclus, and other peaceful nano fish. They should never be housed with larger or predatory species that could easily view them as food. Keeping them in a dedicated species-only aquarium is often the best way to see their natural, uninhibited behavior.

Tank level

Top/Middle

Boraras naevus is a species that primarily occupies the middle and upper levels of the water column. They are active swimmers within these zones, especially when they feel secure in a well-established school. To make them comfortable in the upper areas, the addition of floating plants is highly recommended to diffuse the light. They will rarely venture to the bottom of the tank unless they are searching for food or seeking shelter among low plants.