Marsh Killifish

Fundulus confluentus, the Marsh Killifish, is a small and adaptable killifish from coastal freshwater and brackish marshes of the southeastern United States. The body is pale olive-green with irregular darker blotching, and the species is notable for its tolerance of a wide range of salinities from fresh to slightly brackish water. It is one of several small Fundulus specialised for life in the dynamic salinity fluctuations of coastal marsh environments.

In the aquarium, F. confluentus is straightforward to maintain in a 60 L tank with moderate temperatures. It tolerates a pinch of marine salt if desired, though this is not necessary. The species accepts most foods readily, including flake, frozen, and live invertebrates. Spawning occurs on plants or substrate, with eggs hatching in 10–14 days.

This species appeals to keepers interested in North American coastal biotopes and native fish conservation. Its adaptive physiology and ecological interest make it a more engaging fish than its plain colouration might initially suggest.

Water: 15–28 °C, pH 6.5–8.5, fresh through lightly brackish (0–5 ppt salt tolerated). Tank: 60 L planted tank; occasional salt addition optional but not required. Feeding: Omnivore; accepts flake, frozen, and live invertebrates readily; feed daily. Breeding: Spawns on vegetation; eggs hatch in 10–14 days; fry are robust. Compatibility: Peaceful; mix with other similarly sized, hardy community fish.