AquariumStocking ideas · checked against sources
What fish can go in a 20 gallon long tank?
A standard 20 gallon long tank is 30 × 12 × 12 inches. Of the 106 species in our database, 53 fit comfortably and 7 are a tight fit, based on each species' sourced minimum tank size and group size.
Stocking combinations that pass every check
Each set was run through the tank builder's rules: tank size, temperature, pH, hardness, predation, fin-nipping, temperament and stocking level. Treat them as starting points, not prescriptions.
Stocking about 51% · shared temperature 72–77°F
Open in tank builderStocking about 64% · shared temperature 73–77°F
Open in tank builderStocking about 55% · shared temperature 72–77°F
Open in tank builderFish that fit a 20 gallon long tank
Tetras & rasboras (13)
- Neon Tetra1.4 in adult · group 8+
- Cardinal Tetra1.7 in adult · group 8+
- Harlequin Rasbora2.1 in adult · group 8+
- Ember Tetra0.9 in adult · group 8+
- Chili Rasbora0.9 in adult · group 8+
- Celestial Pearl Danio1 in adult · group 20+
- Glowlight Tetra1.9 in adult · group 6+
- White Cloud Mountain MinnowNeeds care1.9 in adult · group 10+
- Head-and-tail-light Tetra2.1 in adult · group 6+
- Lambchop Rasbora1.4 in adult · group 8+
- Penguin Tetra1.7 in adult · group 6+
- Pristella Tetra2.1 in adult · group 6+
- Silver Tip Tetra2.4 in adult · group 6+
Livebearers (4)
- Guppy2.8 in adult · group 6+
- Platy2.4 in adult · group 6+
- Endler's LivebearerNeeds care1.2 in adult · group 6+
- Variatus Platy2.4 in adult
Barbs (1)
Gouramis & bettas (4)
- Honey Gourami2.6 in adult · group 4+
- Dwarf GouramiNeeds care4.2 in adult
- BettaNeeds care3.3 in adult
- Sparkling Gourami1.9 in adult · group 2+
Cichlids (3)
Catfish & plecos (9)
- Panda Cory2.4 in adult · group 6+
- Pygmy Cory1.4 in adult · group 6+
- Julii Cory2.6 in adult · group 6+
- Sterbai Cory3.2 in adult · group 6+
- Bristlenose Pleco5.9 in adult
- OtocinclusNeeds care1.7 in adult · group 6+
- Clown Pleco4.2 in adult
- Peppered CoryNeeds care3.3 in adult · group 6+
- Upside-down Catfish4.7 in adult · group 3+
Loaches (2)
Shrimp & snails (11)
- Cherry Shrimp1.6 in adult · group 10+
- Amano Shrimp2 in adult · group 6+
- Nerite Snail1 in adult
- Mystery Snail2 in adult
- Assassin Snail1.3 in adult
- Bamboo Shrimp4 in adult · group 6+
- Crystal Red Shrimp1.5 in adult
- Ghost Shrimp2 in adult · group 6+
- Japanese Trapdoor Snail2.6 in adult
- Malaysian Trumpet Snail3.1 in adult
- Ramshorn Snail1.2 in adult
Others (6)
- African Dwarf Frog1.4 in adult · group 2+
- Bumblebee GobyNeeds care1.7 in adult · group 6+
- Clown Killifish1.6 in adult · group 8+
- Dwarf Neon Rainbowfish3.8 in adult · group 6+
- Forktail Blue-eye2.8 in adult · group 8+
- Pea Puffer1.4 in adult
Tight fit (just under a sourced minimum)
Popular fish that outgrow it
- Rummy-nose TetraNeeds 35 in long
- Pearl GouramiNeeds 36 in long / 21 gal
- Bolivian RamNeeds 36 in long / 48 gal
- AngelfishNeeds careNeeds 39 in long / 53 gal
- Zebra DanioNeeds careNeeds 35 in long / 21 gal
- MollyNeeds careNeeds 35 in long / 21 gal
- SwordtailNeeds careNeeds 47 in long / 29 gal
- Boesemani RainbowfishNeeds 48 in long / 29 gal
- Bala SharkOutgrows tanksNeeds 96 in long / 228 gal
- Blood Parrot CichlidOutgrows tanksNeeds 55 gal
- Buenos Aires TetraNeeds careNeeds 35 in long / 21 gal
- Chinese Algae EaterOutgrows tanksNeeds 60 in long / 80 gal
Gear sized for 20 gallon long
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Common questions
How many fish can go in a 20 gallon long tank?
It depends on adult size and waste output, not inches per gallon. The combinations on this page stay under about 80% of a sensible load for 20 gallons in our estimate.
What fish outgrow a 20 gallon long tank?
Popular examples include Rummy-nose Tetra, Pearl Gourami, Bolivian Ram, Angelfish, Zebra Danio, Molly.
What heater size does a 20 gallon long tank need?
About 100 W, using roughly 5 watts per gallon.