Best freshwater fish for a 40 gallon tank

A 40 gallon freshwater tank holds a centerpiece such as a pearl gourami over a school and a cory group. It also opens up three spot gouramis, zebra loaches and hatchetfish. Every fish here is widely sold, rated for community tanks and lists a minimum tank of 40 gallons or less.

Keeping a saltwater tank? Saltwater fish for a 40 gallon tank →

Tank size: 7–40 gal; 7 gal (25 L) to 40 gal (150 L); half the list needs 20 gal (75 L) or more
Temperature: 72–81°F; 22–27°C, most of the list
pH: 6.0–7.5; Most of the list
Difficulty: 73 easy; 63 medium · 4 difficult
Temperament: 102 peaceful; 38 mostly peaceful

140 species

New at this size

What a 40 gallon adds over a 29

The three spot gourami grows to 5.1 inches (13 cm) and lists 30 gallons (115 liters). The upside-down catfish lists the same and swims belly up under wood. Zebra loaches list 37 gallons (140 liters). The Siamese algae eater grows to 6.3 inches (16 cm) on the same minimum. The marbled and common hatchetfish list 32 and 33 gallons (120 and 125 liters) and stay near the surface.

Stocking plans

Three ways to stock a 40 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.

A pearl gourami over rummy-nose tetras
Full
LightComfortableFullHeavyOverstocked
These species overlap at 75–79°F (24–26°C), pH 6.5–7.0.
Open this plan in the stocking calculator
Congo tetras with honey gouramis
Comfortable
LightComfortableFullHeavyOverstocked
These species overlap at 73–81°F (23–27°C), pH 6.0–7.5.
Open this plan in the stocking calculator
Neon rainbowfish over julii cories
Comfortable
LightComfortableFullHeavyOverstocked
These species overlap at 73–79°F (23–26°C), pH 6.5–7.0.
Open this plan in the stocking calculator

By the numbers

Smallest

Largest

Easiest to keep

Most peaceful

Fits a 20 gallon tank

Fits a 30 gallon tank

FAQ

Common questions

How many fish can go in a 40 gallon tank?

A 40 gallon holds a centerpiece such as a pearl gourami over a school and a cory group, as the plans above show. Adult size sets the count, so ten rummy-nose tetras take less room than three pearl gouramis. Check any mix in the stocking calculator before you buy.

Which gouramis fit a 40 gallon tank?

The three spot gourami lists 30 gallons (115 liters) at 5.1 inches (13 cm), and the pearl gourami 29 gallons (111 liters). The honey gourami lists 14 gallons (54 liters) and fits every tank page from 20 gallons up. The dwarf gourami lists 10 gallons (38 liters) and fits all of them.

Is a 40 gallon tank big enough for angelfish?

Angelfish list 53 gallons (200 liters) and grow to 5.9 inches (15 cm), so they start on the 55 gallon page. In a 40 gallon, a pearl gourami is the centerpiece that fits.