Blackspotted Topminnow

Fundulus olivaceus is a surface-oriented killifish found in clear, spring-fed streams and river pools of the south-central United States, particularly the Ozark region and adjacent drainages. Males develop a vivid pattern of scattered black spots on an olive-green body combined with bold dorsal and caudal fin pigmentation, while females are more modestly marked with a lateral stripe. Like all topminnows, it inhabits the water surface, feeding on aquatic and terrestrial insects.

In the aquarium, Blackspotted Topminnows are hardy and active surface fish that appreciate a well-covered tank — they are capable jumpers and a tight-fitting lid is essential. They thrive in small groups with one male and two or three females, or can be combined with other surface-oriented small natives in a mid-sized community tank.

They feed eagerly on floating invertebrates, live or frozen Daphnia, and small insects, and adapt well to quality floating flake and micro-pellet foods. Their constant surface activity and interesting social dynamics, including male display behaviour, make them engaging aquarium inhabitants.

Water: 16–26 °C, pH 6.5–8.0, moderate hardness; gentle to moderate surface flow. Tank: 60 L minimum; heavily covered lid essential; floating plants for cover and surface activity. Feeding: Floating live/frozen Daphnia, small insects, surface micro-pellets, quality flake. Breeding: Adhesive eggs attached to aquatic plants near surface; separate eggs for rearing. Compatibility: Semi-aggressive between males; compatible with small peaceful mid-water natives.