Santos Rivulus (Rivulus santensis) — 3-4cm

Overview

The Santos Rivulus (Rivulus santensis) is a small, peaceful South American rivulus native to tropical freshwater habitats in Brazil. Reaching 3-4cm in length, this species is prized for its compact size, subtle beauty, and interesting breeding behavior. Ideal for nano planted aquariums, Rivulus santensis thrives in soft, slightly acidic water with gentle filtration. Available for sale UK from Tropical Fish Co, this captivating killifish rewards dedicated keepers with unique surface-dwelling behaviour and delicate beauty.

Appearance and Coloration

The Santos Rivulus displays subtle but attractive colouration with a slender, compact body adorned in earthy browns, greens, and soft golds with delicate iridescence. Males are more intensely coloured than females, with more pronounced finnage and subtle highlights that shimmer under subdued lighting. Females are smaller, plumper, and more subdued in colour. The overall appearance is modest but elegant, perfectly suited to a natural planted aquarium. In a tank with dark substrate and tannin-stained water, the subtle colours become more refined and visible.

Natural Habitat

Rivulus santensis is native to South America, where it is associated with tropical freshwater habitats in Brazil. These fish inhabit slow-moving streams, swamps, ditches, and seasonal pools characterised by soft, slightly acidic to neutral, tannin-rich water, dense vegetation, submerged roots, and abundant leaf litter. Water flow is minimal, and the substrate consists of mud, sand, and organic debris. These surface-oriented fish spend most of their time at or near the water's surface.

Aquarium Setup

A minimum 20-litre aquarium is sufficient for a pair or small group of Santos Rivulus. Use a fine sand or smooth gravel substrate with plenty of live plants such as Cryptocoryne, Java moss, Microsorum, and floating species like Salvinia or Pistia. Provide open swimming space near the surface, as this is a surface-oriented species. Add dried leaves (Indian almond or oak) to release tannins and replicate the natural environment. Lighting should be subdued, and filtration gentle to avoid strong currents. A secure, tight-fitting lid is essential, as rivulids can jump.

Feeding and Diet

As a carnivore, Rivulus santensis requires a varied, protein-rich diet to maintain health and colour. Offer small live and frozen foods such as daphnia, brine shrimp, bloodworms, mosquito larvae, and other tiny invertebrates daily. Quality micro-pellets or granules may be accepted once acclimated. This surface-oriented predator is well-adapted to capturing small prey at the water's surface. Feed small portions once or twice daily, removing uneaten food promptly to maintain water quality.

Behaviour and Temperament

The Santos Rivulus is a peaceful, surface-dwelling species that spends most of its time patrolling the upper water column in search of food. Males may display to each other with flared fins and subtle posturing, but serious aggression is rare. These fish are most active during dawn and dusk, and they appreciate a dimly lit aquarium with plenty of surface cover. They are not competitive feeders, so avoid housing them with boisterous or fast-moving species.

Suitable Tank Mates

Rivulus santensis is best kept singly or as a pair/species tank. If tankmates are used, only very small peaceful fish with similar water needs should be considered. Shrimp and tiny invertebrates may be eaten. Avoid large fish, aggressive fish, fin-nippers, very active boisterous species, and large predatory invertebrates. A calm, quiet environment is essential for this delicate killifish to thrive and display natural surface behaviours.

Breeding

This is likely an egg-scattering or substrate-spawning rivulus. Condition a pair with high-quality live foods, then provide spawning media such as Java moss or yarn mops. Provide fine-leaved plants or spawning mops and separate adults from eggs if possible, as eggs may be eaten. Fry should be started on infusoria or other very small live foods, graduating to newly hatched brine shrimp after a few days. Breeding success is highest in soft, slightly acidic water with gentle filtration and abundant fine-leaved plants. Avoid strong current and tankmates large enough to prey on them.

Why Buy from Tropical Fish Co

Tropical Fish Co is a trusted UK supplier of rare and specialist tropical fish, including hard-to-find killifish species like Rivulus santensis. We guarantee healthy, well-conditioned stock, expert care advice, and secure nationwide delivery. Every fish is quarantined and inspected before dispatch, ensuring you receive only the finest specimens. Whether you're setting up a dedicated killifish tank or adding a rare species to your collection, Tropical Fish Co offers unmatched quality and customer service. Order online today and bring the beauty of Brazilian waters into your home aquarium.