What size tank does a African Knife Fish need?

African Knife Fish needs a minimum of 75 gallons, with 113 gallons recommended. They are bottom swimmers.

Is African Knife Fish good for beginners?

African Knife Fish is rated "advanced" difficulty (3/5). Suitable for intermediate fishkeepers.

What fish are compatible with African Knife Fish?

African Knife Fish is semi-aggressive. Compatible tank mates include other semi-aggressive fish with similar water parameters (pH 6.5-7.5, temp 75-82°F). Give adequate territory space.

African Knife Fish

Xenomystus nigri

Family: Notopteridae • Origin: Various

African Knife Fish (Xenomystus nigri) is a semi-aggressive other reaching 12 inches. Can be kept singly. Minimum tank: 75 gallons.

Min Tank

75 gal

Max Size

12"

Temperature

75-82°F

6.5-7.5

Lifespan

14 years

School Size

Solo OK

Swim Level

bottom

Hardness

5-15 dGH

semi-aggressiveadvancedcarnivore

Is African Knife Fish Right for Your Tank?

African Knife Fish is a moderate-care fish rated "advanced" (3/5). Suitable for hobbyists with some experience who can maintain stable water parameters. They need at least 75 gallons — a mid-size tank commitment. Plan your space accordingly.

African Knife Fish is semi-aggressive — they can live with others but may bully smaller or slower fish. Choose tank mates carefully. They are territorial — provide adequate hiding spots and maintain enough space to reduce aggression. Expected lifespan: 14 years with proper care.

Common Mistakes with African Knife Fish

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Relying on a heater without a thermometer

African Knife Fish needs 75–82°F. Heaters malfunction or drift over time — always use a separate thermometer to verify. Temperature swings of even 3–4°F can trigger stress and disease, particularly ich.

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Putting them in a tank under 75 gallons

Many beginners underestimate tank size needs. African Knife Fish requires at least 75 gallons — ideally 113. Cramped tanks lead to stunted growth, aggression, and poor water quality.

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Housing with peaceful nano fish

African Knife Fish is semi-aggressive and territorial — small, peaceful species like neon tetras, endlers, or celestial pearl danios will be stressed, bullied, or eaten. Choose tank mates that can hold their own.