Red Mini Rasbora (Boraras Naevus)

Boraras naevus is a species of miniature freshwater fish formally described in 2011 . Before its scientific description, it was commonly traded under names like Boraras sp. 'red micros' or Strawberry Rasbora . Here is a quick overview of its key characteristics:

 Appearance & Identification

This tiny fish is known for its vibrant coloration, which gives it the common name "Strawberry Rasbora" . The most distinctive feature is the sexual dimorphism, meaning males and females look noticeably different, a trait unique among its closest relatives .

• Males: Display a vivid red body color, especially when in good condition or breeding. They have a prominent, large, oval-shaped black spot on their side, just behind the gill plate. This spot is significantly larger than that of the female. Males also often show red and black pigment along the front edges of their dorsal and anal fins .

• Females: Are generally larger-bodied than males, with a rounder belly. Their coloration is more subdued, appearing less intensely red. The defining dark spot on their flank is much smaller and more circular, roughly the same size as their eye .

• Distinguishing from similar species: Unlike many other Boraras species (like the B. brigittae or B. urophthalmoides), B. naevus does not have a continuous dark stripe running along its side. Instead, it has distinct blotches, with the anterior (front) blotch being the most prominent .

 Natural Habitat & Distribution

• Origin: This species is known only from southern (peninsular) Thailand. The original specimens were collected from a swampy area north of Surat Thani city, within the lower Tapi River drainage on the Gulf of Thailand side of the peninsula .

• Habitat: Boraras naevus inhabits shallow, clear-water environments like swamps and marshes. These areas are typically heavily vegetated with submerged plants and leaf litter. Unfortunately, much of its natural habitat is believed to have been converted into rice paddies .

• Conservation Status: Due to a lack of extensive data on its population and full distribution, the IUCN Red List currently classifies Boraras naevus as Data Deficient .

 Aquarium Care

As a nano fish, the Strawberry Rasbora has specific care requirements to thrive.

• Tank Setup: They are best kept in a densely planted aquarium with plenty of cover. A dark substrate, driftwood, and leaf litter help replicate their natural, tannin-stained habitat. Floating plants are highly recommended to diffuse the light, as they can be timid under bright conditions. Due to their origin in sluggish waters, the filtration should provide gentle water movement .

• Tank Size: While a small group can be kept in a 5-gallon tank, a 10-gallon (45cm in length) or larger is recommended to provide stable water conditions and ample swimming space for a proper school .

• Social Grouping: This is a shoaling species and must be kept in a group. A minimum of 8-10 individuals is essential, but a group of 12 or more is ideal. A larger group will make the fish feel more secure, display more natural behavior, and encourage males to show their best colors .

• Tank Mates: Due to their tiny size and shy nature, they are best kept with other small, peaceful species. Good companions include dwarf shrimp (like Caridina and Neocaridina), pygmy corydoras, Otocinclus catfish, small rasboras like Trigonostigma, and licorice gouramis. Avoid keeping them with larger or boisterous fish .

 Diet and Feeding

In the wild, Boraras naevus is a micropredator, constantly foraging for small insects, worms, and crustaceans . In the aquarium, they will accept high-quality crushed flakes and micro pellets, but these should not be the only food offered. A varied diet with regular servings of small live or frozen foods is crucial for optimal health and coloration. Excellent choices include baby brine shrimp, daphnia, cyclops, and microworms .

 Breeding

Breeding Strawberry Rasboras is possible for a dedicated hobbyist. They are egg-scatterers that show no parental care and will eat their own eggs .

• Setup: A separate breeding tank (10-15 litres) with very dim lighting is recommended. The tank should contain fine-leaved plants like Java moss or spawning mops. To protect the eggs, you can use a mesh or a layer of marbles at the bottom that allows eggs to fall through, out of reach of the adults. The water should be soft and acidic (pH 5.0-6.5) .

• Process: Condition a small group of males and females with live foods. Introduce one or two pairs to the breeding tank. Spawning typically occurs the following morning.

• Fry Care: Remove the adults after a couple of days to prevent them from eating the eggs. The tiny fry will hatch in about 24-36 hours and will first feed on their yolk sacs. Afterwards, they require microscopic foods like infusoria until they are large enough to accept baby brine shrimp