American Flagfish tank mates
A killifish that earns its place eating the hair algae nothing else touches, and charges in fins when the work runs out. Right in a robust unheated set-up; wrong near anything slow or trailing.
Common mistakeBuying flagfish as a peaceful algae crew for a betta tank is the fortnight fin-shred story. They target hair algae, not every algae type, and a bored male will turn on long fins when the job ends. Keep one male per roughly 60 litres with grazing work and short-finned neighbours — or skip the betta pairing. The mistake is hiring a killifish as a polite cleaner.
Each name below opens a pair check with American Flagfish. That check is the decision, not the list itself.
Usually safer companions
Conservative shortlist from this profile. Open a pair page before you buy.
None listed here. Use the pair checker with species you are considering.
Risky or situational
May work with more water, a mature system, or a species-only setup. Read the pair page before you experiment.
Angelfish reaches 20cm and is flagged predatory or as likely to eat small fish. Adult-size American Flagfish at 6cm is inside that gape range. Both species defend territory. The pairing needs a long footprint and rockwork or planting that breaks the sightline between two defended spots. Angelfish is rated semi-aggressive, so expect chasing, fin damage, or display behaviour directed at American Flagfish. Run the pair checker before stocking.
Both species defend territory. The pairing needs a long footprint and rockwork or planting that breaks the sightline between two defended spots. Run the pair checker before stocking.
Marked risky or situational on the profile. Tank length and group size change the outcome more than a temperament label does.
Marked risky or situational on the profile. Tank length and group size change the outcome more than a temperament label does.
Marked risky or situational on the profile. Tank length and group size change the outcome more than a temperament label does.
Marked risky or situational on the profile. Tank length and group size change the outcome more than a temperament label does.
Marked risky or situational on the profile. Tank length and group size change the outcome more than a temperament label does.
Fish to avoid with American Flagfish
Predation, aggression, or space rules on this profile. Treat these as poor default mixes.
Betta conflicts with American Flagfish on temperament, predation, or footprint. The juvenile size in a shop tank is not the figure that matters here.
Tank size and groups
- Published minimum for American Flagfish: 60L. Group minimum 1 .
- Compatibility changes when the tank is too short for turning, too little for a real school, or too warm for one species and not the other. That is why pair checks include tank context, not only temperament.
- Nearest litre hub to this minimum: 60L hub.
Easier alternatives to consider
Hardier first-tank names from the library. Still read the profile. Not a substitute for reading this one.
Plan before you buy
Start a pair check with American Flagfish, or open a starter plan with the top safer companions in the builder.
Tank hubs: 60L
Related reading
Guides that list other fish with the same trait, so you can plan around the group rather than one row.
- Fin-nipping fish →
American Flagfish is on this list. Matters more with long-finned tank mates.
- Fish for smaller tanks →
American Flagfish fits the small-tank filter — check volume hubs before you buy.
Filtration & heating
A 60L minimum tank for American Flagfish needs a filter rated for at least 240L/hr turnover and a heater maintaining 18–28°C.
Similar fish (same category)
- Marbled Hatchetfish · min 60L
- Golden Wonder Killifish · min 80L
- Pea Puffer · min 40L
- Clown Killifish · min 20L
- African freshwater butterflyfish · min 150L
- Ropefish / reed fish · min 200L
- Senegal bichir · min 300L
- Black ghost knifefish · min 500L
Featured compatibility checks
Curated pair pages for American Flagfish. Each opens a full verdict — not just a list label.
American Flagfish tank mates — quick answers
- What fish can live with American Flagfish?
- This hub has no “usually safer” (GOOD) companions for American Flagfish. Workable neighbours sit in caution — for example Angelfish, Bristlenose Pleco, Cherry Shrimp, Guppy, Harlequin Rasbora, Neon Tetra. Treat every name as a pair check, not a shopping list.
- What tank mates should you avoid with American Flagfish?
- Avoid Betta based on size, temperament, or predation risk on this profile.
- What size tank do American Flagfish need for a community?
- 60L is the planning floor for adult swimming space and bioload. A 80L+ tank is the more comfortable long-term footprint. Length and depth matter as much as raw litres for active or territorial fish.