Florida Flag Fish (Jordanella floridae)

The Florida Flag Fish (Jordanella floridae) is a fascinating North American killifish endemic to Florida's freshwater habitats — from swamps, marshes, and ditches to slow-moving streams and springs throughout the state. Unlike most killifish, which are adapted to soft, tropical waters, the Florida Flag Fish inhabits a range of water conditions including somewhat harder, cooler water typical of Florida springs.

Males display exceptional coloration: the flanks show alternating horizontal rows of red-orange and green-blue iridescent scales forming a pattern reminiscent of the American flag, with a prominent dark spot on the central flank. The fins are edged in orange-red. Females are less colorful but share the central body spot and a pale olive base coloration.

The Florida Flag Fish is notable in the aquarium hobby primarily as a natural algae controller. It actively grazes on filamentous algae, hair algae, and thread algae that are difficult to control by other means — making it a practical and attractive solution for planted aquarium algae issues. However, it may also nibble on softer plant leaves and fine-leaved plants if algae is scarce.

As a subtropical species native to Florida, it tolerates a wider temperature range than most tropical fish, including temperatures down to 15°C — making it suitable for unheated indoor tanks in temperate climates and even outdoor pond setups during warmer months.

Florida Flag Fish tolerate a broad range of conditions: pH 6.5–8.5, hardness 5–20 dGH, and temperatures 15–26°C. They are exceptionally hardy and among the most adaptable freshwater aquarium fish. Their subtropical nature means they can be kept without a heater in many temperate indoor environments.

A minimum 60-liter aquarium is recommended for a pair or small group. Provide dense plantings of tougher, broad-leaved plants (Anubias, Java fern) alongside fine-leaved plants where algae growth is desired. Be aware they may graze on fine-leaved plants like mosses if hungry — ensure adequate algae or supplement with spirulina-based foods.

Feed a varied diet incorporating algae-based foods as the primary component: spirulina flakes, algae wafers, blanched vegetables (spinach, zucchini, cucumber). Supplement with high-quality flake, daphnia, and small invertebrates. Their herbivorous tendencies mean spirulina should constitute a significant portion of the diet.

Florida Flag Fish can be kept in pairs or small groups but males are territorial with each other. Maintain a 2:1 or higher female-to-male ratio to distribute male aggression. They are compatible with most community fish but may occasionally be nippy toward long-finned species. Avoid housing with delicate, slow-moving fish.

They are outstanding pond fish for controlling algae in outdoor water garden setups during spring through early autumn. Regular water changes of 25–30% weekly maintain water quality for indoor aquariums.