Least Killifish

Heterandria formosa is a livebearer from the USA (Florida to South Carolina) and one of the smallest vertebrates in North America. Despite the name, it is not a true killifish but a livebearer. Females give birth to only one or two fry at a time but do so almost continuously. It is extremely cold-tolerant and does not require a heater in most European homes.

Water: 18–28 °C, pH 6.5–8.0, soft to hard — very adaptable. Tank: 15 L minimum; heavily planted with floating plants; no lid needed at low stocking. Feeding: Micro pellets, crushed flake, baby brine shrimp, micro worms. Behaviour: Peaceful; females significantly larger than males; can be kept in colonies. Compatibility: Nano shrimp, other small peaceful fish; avoids competing with fast or boisterous species.