Least Rasbora

Least Rasbora, scientifically known as Boraras urophthalmoides, is one of the smallest aquarium fish available for freshwater hobbyists. Its slim body, subtle reddish to copper tones, and signature black tail spot give it a neat, refined look that stands out beautifully in planted nano tanks. Because of its small adult size and calm nature, this species is especially popular among aquascapers and keepers of peaceful community aquariums.

This fish does best when kept in a proper school, where its natural confidence and gentle activity become more visible. In a well-planted aquarium with dark substrate, floating cover, and stable water conditions, Least Rasboras display better colour and more natural behaviour. They are ideal for hobbyists who want a lively but non-aggressive nano species that will not overpower a carefully designed planted setup.

Key Features

• Appearance: A very small, slender rasbora with a delicate body shape and a noticeable dark marking near the tail, often giving it the popular exclamation point rasbora nickname.
• Size: Usually grows to around 2 cm, making it suitable for nano and small planted aquariums when maintained in groups.
• Colors: Soft reddish, orange, or copper body tones may become more visible under calm conditions, subdued lighting, and quality feeding.
• Lifespan: With stable water quality and proper care, they can live for several years in a well-maintained freshwater aquarium.
• Temperament: Peaceful, shy, and schooling by nature. They are best kept with other small, non-aggressive tank mates.
• Water Type: Freshwater fish suited to mature, stable aquariums with gentle filtration and low stress.

Care Requirements

• Tank Size: A tank of at least 30 litres is recommended, though larger planted tanks provide more stable conditions and better schooling behaviour.
• Water Parameters: Best kept at 22-28°C with a pH around 5.5-7.0. Soft to moderately soft water is generally preferred.
• Diet: Accepts finely crushed flakes, micro pellets, and small live or frozen foods such as baby brine shrimp, daphnia, or microworms.
• Tank Mates: Suitable companions include other peaceful nano fish, small shrimp in established tanks, and calm bottom dwellers that will not harass them.
• Schooling Need: Keep them in a group of at least 6 to 10 fish, though larger groups often make them feel safer and display more naturally.
• Care Tips: Use plants, moss, and shaded areas to reduce stress. Avoid strong current, sudden water changes, and large aggressive fish.

Least Rasbora is a smart choice for aquarists building a peaceful nano community or a nature-style planted aquarium. For best results, introduce them into a cycled tank, keep them in groups, and maintain gentle, stable conditions rather than treating them like a hardy beginner throw-in fish.