Best Fish for a 20 Gallon Tank

Every species in our database that fits a 20-gallon tank.

Wondering what fish go in a 20-gallon tank? Below is every species in our database whose minimum tank size fits 20 gallons — then build and check your exact mix with the stocking & compatibility calculator.

Fish that fit a 20-gallon tank

• Assassin Snail (1.0", 5g min, Peaceful)
• Betta (2.8", 5g min, Semi-aggressive)
• Cherry Shrimp (1.5", 5g min, Peaceful)
• Chili Rasbora (0.7", 5g min, Peaceful)
• Dwarf Mexican Crayfish (1.6", 5g min, Semi-aggressive)
• Ghost Shrimp (1.5", 5g min, Peaceful)
• Malaysian Trumpet Snail (1.0", 5g min, Peaceful)
• Mystery Snail (2.0", 5g min, Peaceful)
• Nerite Snail (1.0", 5g min, Peaceful)
• Pea Puffer (1.0", 5g min, Semi-aggressive)
• Ramshorn Snail (1.0", 5g min, Peaceful)
• Amano Shrimp (2.0", 10g min, Peaceful)
• Celestial Pearl Danio (1.0", 10g min, Peaceful)
• Dwarf Gourami (3.5", 10g min, Peaceful)
• Ember Tetra (0.8", 10g min, Peaceful)
• Endler's Livebearer (1.0", 10g min, Peaceful)
• Glowlight Tetra (1.5", 10g min, Peaceful)
• Guppy (2.0", 10g min, Peaceful)
• Harlequin Rasbora (2.0", 10g min, Peaceful)
• Honey Gourami (2.0", 10g min, Peaceful)
• Killifish (Gardneri) (2.5", 10g min, Semi-aggressive)
• Neon Tetra (1.5", 10g min, Peaceful)
• Platy (2.5", 10g min, Peaceful)
• Pygmy Cory (1.0", 10g min, Peaceful)

How to stock it well

Don't just fill 20 gallons to the brim. Pick one or two schooling species (groups of 6+), maybe a single centerpiece fish, and a small cleanup crew. Understocking is far more forgiving for water quality than packing it in.

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