What are some good long living fresh water fish for a 20 gallon tank?

Here are some excellent long-living freshwater fish for a 20-gallon tank:

1. Celestial Pearl Danio (Danio margaritatus)

Lifespan: Up to 5 years

Size: 1-1.5 inches

Water Parameters: pH 6.0-7.0, Hardness 5-20 dGH, Temperature 68-78°F

Temperament: Peaceful, active, schooling

Diet: Omnivore, accepts a variety of foods including small pellets, flakes, brine shrimp, and daphnia

2. White Cloud Mountain Minnow (Tanichthys albonubes)

Lifespan: Up to 5 years

Size: 1-1.5 inches

Water Parameters: pH 6.0-7.0, Hardness 5-20 dGH, Temperature 65-75°F

Temperament: Peaceful, active, schooling

Diet: Omnivore, accepts a variety of foods such as small pellets, flakes, brine shrimp, and daphnia

3. Zebra Danio (Danio rerio)

Lifespan: Up to 5 years

Size: 1-2 inches

Water Parameters: pH 6.0-7.5, Hardness 5-20 dGH, Temperature 65-78°F

Temperament: Peaceful, active, schooling

Diet: Omnivore, accepts various foods like small pellets, flakes, brine shrimp, and daphnia

4. Neon Tetra (Paracheirodon innesi)

Lifespan: Up to 5 years

Size: 1-1.5 inches

Water Parameters: pH 6.0-7.0, Hardness 5-20 dGH, Temperature 72-80°F

Temperament: Peaceful, active, schooling

Diet: Omnivore, consumes small pellets, flakes, brine shrimp, and daphnia

5. Rummy Nose Tetra (Hemigrammus bleheri)

Lifespan: Up to 5 years

Size: 1.5-2 inches

Water Parameters: pH 6.0-7.0, Hardness 5-20 dGH, Temperature 75-80°F

Temperament: Peaceful, active, schooling

Diet: Omnivore, readily takes small pellets, flakes, brine shrimp, and daphnia

6. Green Neon Tetra (Paracheirodon simulans)

Lifespan: Up to 5 years

Size: 1-1.5 inches

Water Parameters: pH 6.0-7.0, Hardness 5-20 dGH, Temperature 72-80°F

Temperament: Peaceful, active, schooling

Diet: Omnivore, consumes small pellets, flakes, brine shrimp, and daphnia

7. Cardinal Tetra (Paracheirodon axelrodi)

Lifespan: Up to 5 years

Size: 1.5-2 inches

Water Parameters: pH 6.0-7.0, Hardness 5-20 dGH, Temperature 72-80°F

Temperament: Peaceful, active, schooling

Diet: Omnivore, accepts small pellets, flakes, brine shrimp, and daphnia

8. Hatchetfish (Carnegiella strigata)

Lifespan: Up to 5 years

Size: 1.5-2 inches

Water Parameters: pH 5.5-7.0, Hardness 5-20 dGH, Temperature 72-78°F

Temperament: Peaceful, active, schooling

Diet: Carnivore, feeds on small insects and live or frozen foods

9. Killifish (Nothobranchius rachovii)

Lifespan: Up to 18 months

Size: 1-1.5 inches

Water Parameters: pH 6.5-7.5, Hardness 5-20 dGH, Temperature 75-80°F

Temperament: Peaceful, active, schooling

Diet: Carnivore, consumes small live foods such as brine shrimp, daphnia, and microworms

10. Endler's Livebearer (Poecilia wingei)

Lifespan: Up to 2 years

Size: 1-1.5 inches

Water Parameters: pH 6.0-8.0, Hardness 5-20 dGH, Temperature 75-82°F

Temperament: Peaceful, active, schooling

Diet: Omnivore, accepts small pellets, flakes, brine shrimp, and daphnia

These small and beautiful species can thrive and live long and healthy lives in a 20-gallon tank with proper water conditions, quality nutrition, and routine tank maintenance.