Walker's Killifish (Aphyosemion walkeri) — 3-4cm

Overview

Walker's Killifish (Aphyosemion walkeri) is a beautifully colored, peaceful West African killifish endemic to the Niger Delta region of Nigeria. This small, graceful species showcases the stunning diversity of the genus Aphyosemion, with males displaying vibrant reds, yellows, and blues in intricate patterns that intensify during breeding displays. Reaching just 4 cm in length, Walker's Killifish is ideally suited to planted nano and species aquariums where its delicate beauty and fascinating behavior can be fully appreciated. Though classified as moderately difficult due to specific water and dietary requirements, dedicated aquarists are rewarded with a captivating fish that epitomizes the charm of West African killifish. Available for sale UK through specialist suppliers, this species is perfect for those seeking a unique, lesser-known gem for their collection.

Appearance and Physical Characteristics

Walker's Killifish exhibits pronounced sexual dimorphism, with males far more colorful than females. Males display a base coloration of greenish-blue to turquoise on the body, overlaid with red or orange-red vertical bars or spots that create a striking checkerboard or striped pattern. The unpaired fins—especially the dorsal and caudal fins—are elongated and ornately patterned with red, yellow, and blue markings, often with contrasting edging. The anal fin may show extended rays or filaments in well-conditioned specimens. Females are considerably plainer, with a brownish or olive body color, rounded fins, and minimal patterning, though they possess a subtle beauty of their own. Both sexes have a slender, pike-like body shape with an upturned mouth adapted for surface feeding, and large, expressive eyes. Coloration intensity in males varies with mood, health, and breeding condition, becoming most vivid during courtship.

Natural Habitat and Distribution

Aphyosemion walkeri is endemic to the Niger Delta in southern Nigeria, where it inhabits shallow, slow-moving forest streams, swamps, and rain pools within shaded, densely vegetated areas. These habitats are characterized by soft, acidic, tannin-stained water with a substrate of leaf litter, peat, and decaying organic matter. Water levels fluctuate seasonally, and during the dry season many pools shrink significantly or dry up entirely, placing selective pressure on killifish to breed opportunistically and tolerate variable conditions. The dense overhead canopy filters sunlight, creating dim, dappled lighting conditions, while submerged roots, fallen branches, and aquatic vegetation provide cover and spawning sites. Water chemistry is typically very soft (0-4 dGH) and acidic (pH 5.0-6.5), with warm temperatures year-round. Replicating these conditions in captivity is key to maintaining health and encouraging natural behaviors.

Aquarium Setup and Environment

A minimum aquarium capacity of 60 liters is recommended for a small group or pair of Walker's Killifish, though species tanks of 40-60 liters are ideal for focused breeding projects. The tank should be densely planted with fine-leaved species such as Cabomba, Myriophyllum, or Ceratophyllum, supplemented with floating plants like Salvinia or Pistia to diffuse lighting and provide cover. Include spawning mops (wool or synthetic yarn tied to cork or weighted) as egg deposition sites. A dark, fine substrate (sand or dark gravel) helps reduce stress and enhance coloration, while driftwood and dried leaves (such as Indian almond or oak) replicate the natural tannin-rich environment and provide additional cover. Filtration should be gentle—sponge filters or low-flow internal filters are ideal to avoid strong currents that stress these calm-water species. A tight-fitting lid or cover glasses are absolutely essential, as killifish are notorious jumpers and will escape through the smallest gaps.

Water Parameters and Quality

Walker's Killifish require soft, slightly acidic water to thrive and display their best colors. Maintain temperatures between 22-26°C, with 24°C being ideal; avoid temperatures above 27°C, as killifish can be sensitive to heat stress. The pH should range from 5.5-7.0, with a preference for the lower end (5.8-6.5). Water hardness must be soft, ideally 0-6 dGH; use rainwater, RO water, or deionized water remineralized with appropriate buffers if tap water is too hard. Stability is critical—sudden fluctuations can trigger stress and disease. Maintain zero ammonia and nitrite at all times, and keep nitrates below 20 ppm through regular small water changes (15-20% weekly). The addition of peat filtration or blackwater extracts can help replicate natural conditions and support health. Good water quality is non-negotiable for this sensitive species.

Feeding and Nutrition

Aphyosemion walkeri is a strict carnivore, and in the wild feeds almost exclusively on small aquatic and terrestrial insects, insect larvae, and microcrustaceans at the water surface. In captivity, live and frozen foods form the cornerstone of a successful diet: offer daphnia, cyclops, brine shrimp (enriched with spirulina for color enhancement), mosquito larvae (black and white), grindal worms, and microworms daily. Bloodworms can be fed 2-3 times per week but should not dominate the diet, as they are rich and can cause digestive issues if overfed. High-quality micro pellets or freeze-dried foods may be accepted once fish are settled, but live and frozen foods are strongly preferred and essential for maintaining condition and encouraging breeding. Feed small portions 2-3 times per day, as killifish have small stomachs and fare better with frequent small meals than large, infrequent feedings.

Behaviour and Temperament

Walker's Killifish are peaceful and somewhat shy by nature, spending much of their time in the upper and mid-water levels of the aquarium, often hovering motionless among plants before darting forward to capture food. Males can be territorial toward one another, especially in smaller tanks, displaying to rivals by spreading fins and performing lateral displays, though serious aggression is rare. A pair or small group with multiple females per male (1 male to 2-3 females) works best to distribute male attention and reduce stress on individual females. These fish are most active during dawn and dusk, becoming bolder in dimly lit aquariums. They are not schooling fish but appreciate the presence of their own kind and will interact through subtle displays and movements. Their calm demeanor makes them unsuitable for busy community tanks where fast, boisterous fish will outcompete them for food or cause stress.

Tank Mates and Compatibility

Walker's Killifish are best kept in a dedicated species tank where their delicate nature and specific requirements can be fully accommodated. If tankmates are desired, they must be very small, peaceful, and non-competitive—species such as microrasboras (Boraras species), small peaceful tetras (e.g., ember tetras), or Corydoras pygmaeus may coexist in larger, heavily planted setups. However, even these companions can outcompete killifish for food, so careful observation during feeding is essential. Avoid all large or boisterous fish, fin-nippers (even small barbs or tetras), aggressive cichlids, fast competitive feeders, and predatory species. Shrimp and snails may coexist, though very small shrimp or fry may be eaten. The safest and most rewarding approach is a species-only tank where Walker's Killifish can be the stars, displaying natural behaviors without stress or competition.

Breeding

Aphyosemion walkeri is an egg-scattering annual or non-annual killifish (depending on locality) that can be bred successfully in captivity with proper preparation. Condition breeding pairs or groups with high-quality live foods for 2-3 weeks, then place them in a dedicated breeding tank (20-40 liters) with soft, acidic water (pH 5.5-6.0, temperature 24-25°C), gentle sponge filtration, and dim lighting. Provide spawning mops (fine wool or synthetic yarn) or fine-leaved plants such as Myriophyllum as egg deposition sites. Pairs will spawn over several days, depositing a few eggs daily among the mop fibers or plant leaves. Eggs are non-adhesive and should be collected regularly (every 2-3 days) by removing the mop and gently rinsing eggs into a shallow container. Incubate eggs in shallow water (2-3 cm depth) with methylene blue or a mild antifungal treatment to prevent fungus. Eggs typically hatch in 10-21 days depending on temperature. Fry are very small and require infusoria or liquid fry food initially, progressing to newly hatched brine shrimp and microworms after 5-7 days. Growth is slow, and water quality must be pristine to avoid losses.

Why Buy from Tropical Fish Co

Tropical Fish Co is the UK's trusted source for rare and specialist killifish species, including healthy, acclimatized Walker's Killifish from reputable breeders. Every fish is quarantined, carefully conditioned on live and frozen foods, and health-checked before dispatch to ensure you receive vigorous, disease-free specimens. Our expert team provides detailed care guides, personalized setup advice, and ongoing support to help you create the ideal soft-water, planted environment these beautiful fish deserve. We offer a live arrival guarantee on all orders, with secure, insulated packaging and next-day courier delivery to your door. Whether you're new to killifish or an experienced breeder, our commitment to quality, ethical sourcing, and customer service ensures you receive the finest livestock available. Order your Walker's Killifish today and discover the joy of keeping one of West Africa's most beautiful aquarium gems.