Best freshwater fish for a 20 gallon tank

A 20 gallon freshwater tank fits one school of small fish, a group of small cories and a single centerpiece. Every fish here is widely sold, rated for community tanks and lists a minimum tank of 20 gallons or less. The three plans below were checked in the stocking calculator, which counts adult size and each species' minimum tank.

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Tank size: 7–20 gal; 7 gal (25 L) to 20 gal (76 L); half the list needs 15 gal (55 L) or more
Temperature: 72–81°F; 22–27°C, most of the list
pH: 6.0–7.5; Most of the list
Difficulty: 58 easy; 45 medium · 3 difficult
Temperament: 82 peaceful; 24 mostly peaceful

106 species

New at this size

What a 20 gallon adds over a 10

The neon tetra lists 11 gallons (40 liters), just over a 10 gallon tank, so a 20 gallon is where a school of them fits. The cherry barb, marked beginner, and the honey gourami, marked easy, both list 14 gallons (54 liters). The bristlenose pleco grows to 4.9 inches (12.5 cm) and lists 20 gallons (75 liters), as do the clown pleco and the queen arabesque pleco. Sterba's and Adolfo's cories list 20 gallons (75 liters) too. The neon rainbowfish, 3.1 inches (8 cm) and marked medium, lists 20 gallons (76 liters).

Stocking plans

Three ways to stock a 20 gallon tank

Each plan below ran through the stocking calculator, which reads every fish at its adult size against its minimum tank. Open one to change the counts or swap in your own fish.

Neon school with a dwarf gourami
- 10Neon tetra
- 6Panda cory
- 1Dwarf gourami
Comfortable
LightComfortableFullHeavyOverstocked
These species overlap at 72–77°F (22–25°C), pH 6.0–7.5.
Open this plan in the stocking calculator
Nano fish with a shrimp colony
- 10Ember tetra
- 8Pygmy cory
- 10Cherry shrimp
- 1Zebra nerite
Comfortable
LightComfortableFullHeavyOverstocked
These species overlap at 72–79°F (22–26°C), pH 6.5–7.0.
Open this plan in the stocking calculator
Cherry barbs over panda cories
Comfortable
LightComfortableFullHeavyOverstocked
These species overlap at 72–77°F (22–25°C), pH 6.5–7.5.
Open this plan in the stocking calculator

By the numbers

Smallest

Largest

Easiest to keep

FAQ

Common questions

How many fish can go in a 20 gallon tank?

The count depends on adult size, so a 20 gallon holds far more ember tetras than swordtails. The plans above range from a neon school with a dwarf gourami to a nano tank with a shrimp colony. The old inch-per-gallon rule undercounts small fish and overcounts heavy-bodied ones. Run your own mix through the stocking calculator, which checks each fish against its minimum tank.

Which popular fish need more than a 20 gallon tank?

Angelfish list 53 gallons (200 liters), and Bolivian rams and scissortail rasboras list 45 gallons (170 liters). Blue acaras and yoyo loaches list 42 gallons (160 liters). Common goldfish list 50 gallons (190 liters) and grow to 9.8 inches (25 cm). Congo tetras and mollies list 24 gallons (90 liters), so they start on the 29 gallon page.

Can a pleco live in a 20 gallon tank?

A bristlenose pleco can, at 4.9 inches (12.5 cm) and a 20 gallon (75 liter) minimum. The common pleco sold as an algae eater is usually the Amazon sailfin catfish. It grows to 17.7 inches (45 cm) and lists 100 gallons (380 liters).

Can a 20 gallon tank hold shrimp with fish?

Cherry shrimp list 5 gallons (19 liters) and share the second plan above with ember tetras and pygmy cories. Gouramis eat dwarf shrimp like these, so that plan keeps the colony with nano fish only.

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