Should I buy it?
American Flagfish
Jordanella floridae
Typical trade / ID note: Jordanella floridae
Also known as: flagfish, florida flagfish, Flagfish, Florida flagfish
Fishori provides conservative planning guidance, not guarantees.
Based on typical aquarium care sources; details may vary between setups. Use the numbers here as planning defaults — your room, water, and routine still shape real-world outcomes.
A working algae-crew killifish for temperate tanks. Eats hair algae, nips fins. Pair with corys and rasboras, never with shrimp or bettas.
Best for
Temperate planted tanks 60L or more wanting hair algae removal from an active fish that earns its place. Works well with corydoras.
Avoid if
You keep bettas, shrimp, or any slow long-finned fish. American flagfish nip fins as a default behaviour.
Top things that go wrong
- Fin-nipping risk in typical community layouts. Fin-nipping risk toward long-finned or slow tank mates when the school is understocked, bored, or kept in a tank too short to spread out in.
- Shrimp & snails. Shrimp: depends on the individual fish. Some leave them alone, others hunt cherry shrimp down within a week of meeting them.
Common mistakeExpecting flagfish to eat all algae types. They target hair algae aggressively but ignore green spot algae and most film algae.
What most shops don't tell you
- 1.Bought as a peaceful algae crew for a betta tank. The flagfish eats the betta's fins within a fortnight.
- 2.Solo male in a clean tank. Without hair algae to eat or a female to display at, the male turns on slower tank mates.
- 3.A real algae crew fish for the temperate community. Wants room-temperature water (18 to 26 C works), eats hair algae other species ignore, and nips fins of anything slower than itself. Skip bettas, fancy guppies, and shrimp colonies.
About this species
American flagfish are 6 cm North American killifish with red, blue, and yellow bands that read like a small flag. The species eats hair algae and blackbeard aggressively, which makes it a working algae crew member in a robust tank. Males are confirmed fin nippers.
- Marbled Hatchetfish60L min · same group, comparable tank size
- Golden Wonder Killifish80L min · same fish family
- Pea Puffer40L min · same group, similar adult size
- Clown Killifish20L min · same group, similar adult size
- African freshwater butterflyfish150L min · same fish family
- Ropefish / reed fish200L min · same fish family
- Senegal bichir300L min · same fish family
- Black ghost knifefish500L min · same fish family
- Agassiz’s dwarf cichlidalso intermediate semi-aggressive, similar tank size
- Apistogramma Borelliialso intermediate semi-aggressive, similar tank size
- Apistogramma Macmasterialso intermediate semi-aggressive, similar tank size
- Apistogramma Trifasciataalso intermediate semi-aggressive, similar tank size
- Cockatoo / crested Apistogrammaalso intermediate semi-aggressive, similar tank size
- Golden Wonder Killifishalso intermediate semi-aggressive, similar tank size
No reverse lookups on file yet.
Plan grid
Key limits are shown above; this section adds planning detail: pH band, swim level, bioload and activity, and the radar.
Swim zones
Planning trait chart
Six indices for comparing species on paper before you spend.
- Beginner ease38
- Peacefulness22
- Community fit0
- Small-tank fit100
- Hardiness54
- Energy54
Numbers are deterministic planning indices from Fishori fields — not a scientific score of your individual fish.
Common setup sketches
Conservative patterns from Fishori fields — still run the pair checker for every species you add; sketches are not a stocking guarantee.
Avoid “one of everything” baskets — American Flagfish belongs in a plan built around territory, line-of-sight breaks, and matched water chemistry.
Tank mate intelligence
Use the "Often compatible" lists as a shortlist, not a stocking plan. Always run the pair tool and check the footprint of your actual tank first. Verify behaviour for American Flagfish against your own reading before you buy.
Pair-level compatibility with this fish as anchor.
Read the blocking rule on each pair page before experimenting.
Do-not-stock combinations on conservative hobby rules.
Compare with
Run a real pair check: American Flagfish + Corydoras Catfish
Behaviour, temperament, and what to watch
Prose and lists come from the same record: read temperament first, then glass-level signals so you are not surprised after day three.
American Flagfish is semi-aggressive: stable in a calm tank, pushy with weaker fish when stressed or crowded. Fin-nipper when the school is understocked, bored, or kept in a tank too short to spread out in. Holds territory on substrate, in caves, or at the surface film. Break the sight lines with hardscape to keep the resident off the visitor.
Stress / aggression triggers on file
- long-finned tank mates
- lack of algae
- spawning sites
Fin nipping: Fin-nipping risk toward long-finned or slow tank mates when the school is understocked, bored, or kept in a tank too short to spread out in.
Predation: Not a predator toward similarly-sized community fish. The usual community caveats about mouth size still apply for very small fry or shrimp.
Territory: Holds territory on substrate, in caves, or at the surface film. Break the line of sight with hardscape, and avoid placing the tank where the fish can see its own reflection.
Planted tanks: good — easy plant ideas
In the glass: typical and warning signs
- Moderate pacing — not hyperactive, not motionless.
- Clamped fins, gasping at the surface, hiding non-stop, or refusing food after the first week.
- Rapid breathing when parameters swing — fix ammonia/nitrite first, then reassess mates.
- Chasing one individual repeatedly, torn fins on tank mates, or food theft every feed.
- Corner guarding, flaring, or body-blocking — territory is normal until it becomes relentless.
- Separate or rehome if injuries appear, one fish is pinned, or feeding becomes a daily chase.
- If water is stable but behaviour worsens, reduce stocking or remove the highest-impact species first.
Fish behaviour can vary between individuals and tank setups. Always observe new fish closely after introduction.
Care parameters: water, food, inverts, grouping
Chemistry and group rules sit here so you are not re-reading the same line from tank mate or temperament blocks. Swim level is in the plan grid above.
Hardness
medium
Diet
herbivore
Vegetable matter, algae, and plant-based prepared foods. Long-term protein-only feeding causes bloat in herbivorous species.
Shrimp & snails
Shrimp: depends on the individual fish. Some leave them alone, others hunt cherry shrimp down within a week of meeting them.
Solo, pair, or one male with two females. Two males in under 100L fight to a clear winner.
Breeding behaviour depends on the species. Research before you buy a mixed-sex group of this fish.
- Hair algae or biofilm in the tank, or a vegetable supplement (blanched courgette, algae wafers) ready.
- Tank mates without trailing fins. Robust community fish work; nano tetras and shrimp do not.
- A 60L+ tank with cover lines so a spawning male holds his corner.
- Acceptance of the temperate tolerance: this species does better with no heater than at 28 C.
- Tank volume meets or exceeds 60L published minimum for adults.
- Heater can hold 18–28°C without cooking cooler-water tank mates.
- No known fin-nippers paired with long-finned fish unless you accept documented risk.
Explore and stocking hubs
Same library as the rest of Fishori: tank-mate index for this species, category peers, guides, and litre-based stocking lists where min tank on file is within the hub volume.
Plan with tools
Pair-level rules and multi-fish stocking use the same conservative engine — add this fish in the tank builder only after mates pass pair checks.
Filtration & heating
A 60L minimum tank needs a filter rated for at least 240L/hr turnover and a heater to hold 18–28°C reliably.
Plant suggestions
American Flagfish does well in planted tanks. Plants compatible with 18–28°C and pH 6.5–8:
Profile status: partially verified · Evidence tier: medium · 2 linked source(s). Fishori does not fabricate citations.
Fishori uses conservative planning rules based on these sources.
Confidence is explained in the summary at the top of this page (same tier as here), not repeated below.
How Fishori evaluates compatibility (same logic as pair and tank tools).
- Seriously Fish. Jordanella floridae
Primary: species page covering Florida range, temperate temperature tolerance, hair-algae diet, and the strong male territoriality at spawning.
- Aquarium Co-Op. American Flagfish Care
Secondary: retailer guide on the algae-eating role and the long-fin warning.
Evidence notes
- Flagfish handle 18 to 22 C steadily, which makes them a candidate for unheated planted tanks in temperate rooms. Tropical 28 C tanks shorten their lifespan.
- Hair-algae appetite is real but not unconditional. A flagfish in a clean tank with no algae turns on plant leaves and slow-moving fish out of frustration.
- Fishori profiles work from typical aquarium trade sizes and hobby care norms. Specialist site checks and literature review for this species are not yet recorded here, so the ranges on this page are planning numbers rather than guarantees.