Micros Rasbora

Geographic Origin and Biotope: Native exclusively to the swampy basins of northeastern Thailand, particularly in the Mekong River basin. Prefers clear swamps densely covered with vegetation or marshes adjacent to rice paddies.

Taxonomy and Morphology: Three-spot Dwarf Rasbora (Boraras micros). The smallest member of the Boraras genus and among the smallest vertebrates in the world (max 13-15 mm / 0.5-0.6 inches). Almost transparent body, fragile in appearance but extremely snappy.

Social Behavior: Obligate gregarious. Forms compact schools that move in unison. The absence of conspecifics (less than 15 specimens) generates a state of perpetual panic. It is totally ignorant towards other species if not to flee.

Coloration and Sexual Dimorphism: Lacks the bright red hues of its cousins. The body is translucent-yellowish with three tiny black spots (behind the operculum, in the center and on the caudal base). Dominant males may show slight reddish margins on the anal and dorsal fins.

Aquarium Setup: A 20-30 liters (5-8 gallons) tank is a "palace" for them. Requires fine sand, abundant mosses and extremely filtered light. Does not need acidic "blackwater" but thrives in neutral or slightly soft waters typical of the Mekong basin.

Diet and Feeding: Micro-predator. Its size prohibits almost all commercial feeds. Must be fed twice a day with Paramecia, Rotifers, tiny microworms and Artemia nauplii. Commercial powder serves only as a "Plan B".

Water Quality: Being so small, ecosystem stability is everything. A sudden drop in pH or a nitrite peak will wipe out the entire school in a few hours. Very small but very frequent water changes so as not to cause osmotic shocks.

Compatibility and Tankmates: It is too small even to live peacefully with Corydoras panda or small Tetras. The only safe pairing is with shrimp or small snails. Cohabitation with Bettas or angelfish is equivalent to providing them with live food.

Aquarium Reproduction: They scatter 1-2 transparent eggs a day among the moss. If the parents are well fed they will not eat their own eggs. The real problem is feeding the fry: Infusoria ("green water") is needed for the first weeks of life.

Risks and Diseases: Very rare in the trade. Often accidentally imported in batches of other rasboras. At risk of malnutrition due to aquarists administering food that is too large (flakes not crushed properly).