Four-Spot Merry Widow (Phallichthys quadripunctatus)

The Four-Spot Merry Widow (Phallichthys quadripunctatus) is a rare freshwater livebearer that offers something genuinely different for aquarium enthusiasts. Native to Costa Rica, this small, peaceful species is recognized for the distinctive dark markings along its body, including the spots that give it its common name. Its understated coloration and unusual appearance make it especially appealing to aquarists interested in lesser-known livebearing fish. Unlike the familiar guppies, mollies, and platies found in most aquarium stores, the Four-Spot Merry Widow is seldom encountered in the aquarium hobby. Its limited availability makes it an exciting addition for enthusiasts who appreciate uncommon species, natural coloration, and the opportunity to maintain a fish that is rarely offered for sale. Our Four-Spot Merry Widows are offered in Locally Bred and USA Bred sourcing variants, depending on availability. Our current offering is Locally Bred, raised by a domestic breeder rather than collected from the wild. These captive-bred fish provide an opportunity to enjoy and help maintain a distinctive livebearing species within the aquarium hobby. What We Love About This Fish A Rare Livebearer: An uncommon species that stands apart from the guppies, mollies, and platies typically available in the aquarium trade. Distinctive Natural Markings: Dark spots and subtle body coloration give the Four-Spot Merry Widow a unique appearance. Peaceful Community Potential: A small livebearer well suited to thoughtfully planned aquariums with compatible, non-aggressive fish. Captive-Bred Availability: Locally Bred and USA Bred sourcing options support the continued availability of this difficult-to-find species. Quick Care Guide Care Level: Moderate – A peaceful but uncommon livebearer that benefits from stable water conditions, a mature aquarium, and careful tank mate selection. Temperament: Peaceful – Generally non-aggressive toward similarly sized fish, although males may display and compete for female attention. Diet: Omnivore – Accepts high-quality micro pellets, finely crushed flakes, small live or frozen foods, and naturally occurring microorganisms. Maximum Adult Size: Approximately 1.5–2 inches (3.8–5 cm), with females generally growing larger than males. Minimum Tank Size: 15 gallons – Provides swimming space and room for a small breeding group. A 20-gallon long aquarium is recommended for larger groups. Swimming Zone: Middle to Upper – Explores planted areas and open swimming spaces while foraging throughout the aquarium. Schooling Requirement: Social Group – Keep at least 6 individuals when possible, preferably with more females than males. Four-Spot Merry Widows are social livebearers rather than tightly schooling fish. Origin: Costa Rica, Central America – Naturally inhabits freshwater environments with aquatic vegetation and relatively gentle water movement. Approximate Purchase Size: Varies by availability – Juvenile and subadult specimens may be offered depending on the breeding source and current inventory. Recommended Water Parameters & Aquarium Requirements The Four-Spot Merry Widow (Phallichthys quadripunctatus) thrives in a mature freshwater aquarium with stable water chemistry, gentle water movement, and plenty of aquatic vegetation. Unlike some of the more adaptable livebearers commonly found in the hobby, this uncommon species benefits from consistent conditions and careful attention to water quality. Water Parameters Temperature: 72–79°F (22–26°C) A stable temperature within this range supports normal activity, feeding, and reproduction. Avoid sudden temperature fluctuations. pH: 7.0–8.0 Neutral to moderately alkaline water is a practical starting point for maintaining Four-Spot Merry Widows. Stability is more important than attempting to achieve an exact pH. General Hardness (GH): 6–15 dGH Moderately mineralized water provides a reasonable starting range for this livebearing species. When available, match the conditions used by the breeder. Carbonate Hardness (KH): 3–10 dKH Adequate carbonate hardness helps maintain stable pH and reduces the likelihood of sudden changes in water chemistry. Ammonia & Nitrite: 0 ppm Both should remain undetectable in an established, properly maintained aquarium. Nitrate: Below 20 ppm Preferred Regular water changes, appropriate stocking levels, and healthy plant growth help maintain good water quality. Aquarium Requirements Minimum Aquarium Size: 15 Gallons A 15-gallon aquarium provides room for a small group, while a 20-gallon long aquarium offers additional swimming space and greater flexibility for maintaining a breeding colony. Filtration & Water Movement Use gentle to moderate filtration that provides biological filtration and oxygenation without creating excessive current. Sponge filters and adjustable-flow filters are suitable choices. Aquatic Plants & Shelter Dense plant growth, floating vegetation, and fine-leaved plants provide security for adults and hiding places for newborn fry. Leave open areas for swimming and feeding. Substrate & Lighting Fine gravel or sand works well, particularly when combined with planted areas. Moderate lighting supports plant growth while shaded areas help the fish feel secure. Aquarium Maturity & Stability Introduce Four-Spot Merry Widows only to fully cycled aquariums. Consistent maintenance and gradual changes in water conditions are especially important when keeping uncommon livebearers. Group Size & Social Structure Maintain a small group rather than a single fish. When keeping both sexes, a female-heavy ratio helps distribute male courtship attention and supports more natural social behavior. Aquatic Arts Tip Ask about the breeder's water parameters when acquiring Four-Spot Merry Widows. Because this species is rarely available and typically maintained through small captive-breeding programs, matching the conditions in which the fish were raised can be more valuable than chasing a narrowly defined set of numbers. Make any necessary adjustments gradually.