American flagfish care

Jordanella floridae · Florida, United States

American flagfish (Jordanella floridae) — Shown: a wild female in a collecting jar; males carry red stripes. Photo: nat_t (iNaturalist), CC0, via Wikimedia Commons

Flagfish are a native Florida killifish that graze hair algae and handle unheated tanks (65 to 79 °F).

Tank size: 20 US gal or larger
Temperature: 65 to 79 °F (18 to 26 °C)
Group size: Alone or in a pair
Temperament: Semi-aggressive
Adult size: 2.5 in
pH: 6.5 to 8.5
Hardness (GH): 8 to 20 dGH
Lifespan: 2 to 3 years
Diet: Omnivore that eats algae including hair algae, flakes, frozen foods
Care level: Easy

In a 20 gallon long

30¼ × 12½ × 12¾ in outside

Drawn to scale: one American flagfish at adult size (2.5 in) in the smallest listed tank that suits them. Choose your tank on the home page to see them in it.

How to keep American flagfish

Flagfish are a native Florida killifish that graze hair algae and handle unheated tanks (65 to 79 °F). Keep one male with females in a 20 gallon or larger planted tank; males defend a patch and nip long fins.

Diet: Omnivore that eats algae including hair algae, flakes, frozen foods. Fish food types compared · how often to feed.

Where they swim: Middle of the tank.

American flagfish tank mates

Share the temperature and water, and neither side eats, nips or bullies the other. Check the full group in the stocking checker.

Dwarf chain loach

2.5 in · 20+ gal · 75–82 °F

Julii corydoras

2.5 in · 20+ gal · 72–79 °F

Drawing

Golden pencilfish

2.6 in · 15+ gal · 75–82 °F

Pearl danio

2.6 in · 20+ gal · 68–77 °F

Sterbai corydoras

2.6 in · 20+ gal · 74–82 °F

Gardneri killifish

2.6 in · 10+ gal · 72–79 °F

Bumblebee catfish

2.4 in · 20+ gal · 70–77 °F

Lyretail killifish

2.4 in · 10+ gal · 70–79 °F

Keep apart

Guppy: American flagfish nip long fins like those of guppies.
Betta: American flagfish nip long fins like those of bettas.
Angelfish: American flagfish nip long fins like those of angelfish.
Pea puffer: Pea puffers belong in a tank of their own.
Fancy goldfish: American flagfish nip long fins like those of fancy goldfish.
African dwarf frog: African dwarf frogs are slow and get bullied or outcompeted by American flagfish.

What an American flagfish tank needs

A tank of 20 US gallons or more (such as the 20 gallon long) with a cover, and the equipment below. American flagfish are comfortable at room temperature, so a heater is optional in a normal home.

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Aqueon PRO QuietFlow Power Filter 10

Rated by the maker for up to 20 US gal, which covers a 20 gallon American flagfish tank without being built for a far bigger one.

Details and fit →

Aqueon QuietFlow Internal Power Filter 15–30 gal

Rated by the maker for 15–30 US gal, which covers a 20 gallon American flagfish tank without being built for a far bigger one.

Details and fit →

API Freshwater Master Test Kit

Tests ammonia, nitrite, nitrate and pH, the readings that matter most before and after adding American flagfish.

Details and fit →Check price on Amazon

Seachem Prime 100 mL

Removes chlorine and chloramine from tap water at every water change.

Details and fit →Check price on Amazon

Fluval Edge Thermometer

Shows the water temperature at a glance, so you know it stays within 65 to 79 °F.

Details and fit →Check price on Amazon

More choices, each with the reason it is in or out: Filters for a 20 gallon tank. We don’t list fish food: any good brand of the foods under Diet will do. Plan the whole tank's equipment →

Common American flagfish problems

Two males fight in a small tank; keep one male per 20 gallons.

Test the water first whenever fish look unwell: see what your readings mean, then match the symptom. For disease, a vet who treats fish can diagnose it and advise treatment.

More to compare

Fish for a 20 gallon tank Shrimp-safe fish Cold-water fish Algae eaters Centerpiece fish Fish for hard water Types of killifish

Clown killifish

1.4 in · 5+ gal

Lyretail killifish

2.4 in · 10+ gal

Gardneri killifish

2.6 in · 10+ gal

Golden wonder killifish

4 in · 20+ gal

Sources

Name, origin and adult size checked against Wikipedia: Jordanella floridae. Temperature, pH, hardness, group size, lifespan and minimum tank size are common hobby guidance, not figures from that article. Ranges are the range the species tolerates; aim for the middle. Minimum tank sizes are for an adult group. Drawings are our own; photo credits follow.

Photo credits

Real photographs from Wikimedia Commons, resized and cropped to fit; each is used under the license named.

American flagfish nat_t (iNaturalist), CC0, via Wikimedia Commons
Dwarf chain loach Stefan Maurer, CC BY-SA 2.0, via Wikimedia Commons
Julii corydoras Bob Jenkins, CC BY 2.0, via Wikimedia Commons
Pearl danio Павлик Лисицын, CC BY 4.0, via Wikimedia Commons
Sterbai corydoras Matthew Mannell, Public domain, via Wikimedia Commons
Gardneri killifish Tommy Kronkvist, CC BY-SA 4.0, via Wikimedia Commons
Bumblebee catfish CHUCAO, CC BY-SA 4.0, via Wikimedia Commons
Lyretail killifish Alexander Prokoshev, CC BY-SA 3.0, via Wikimedia Commons
Guppy Marrabbio2, CC BY-SA 3.0, via Wikimedia Commons
Betta ivabalk (Pixabay), CC0, via Wikimedia Commons
Angelfish Citron, CC BY-SA 3.0, via Wikimedia Commons
Pea puffer Beta Mahatvaraj, CC BY-SA 4.0, via Wikimedia Commons
Fancy goldfish Benson Kua, CC BY-SA 2.0, via Wikimedia Commons
African dwarf frog Stuart Halliday, CC BY 3.0, via Wikimedia Commons
Clown killifish Dornenwolf, CC BY 2.0, via Wikimedia Commons
Golden wonder killifish Marrabbio2, CC BY-SA 3.0, via Wikimedia Commons