20-Gallon Tank Setup: What to Buy and What Fits
A 20-gallon tank is where a true community becomes possible: a school in the middle, a group of corydoras on the bottom and a centerpiece fish. It is also far more forgiving than a 10-gallon, because the larger water volume changes more slowly.
- Dimensions
- 24 × 12 × 16 inlength × width × height
- Weight when full
- ~225 lbswater, substrate, gear
- Heater
- 75 wattsfor 76°F in a 68°F room
- Substrate
- 25 lbsfor a 1.5 inch layer
3 stocking ideas for a 20-gallon tank
Each one passes our checks for tank size, group size, temperature and temperament. Open one in the builder to adjust it.
Classic community
A school above and catfish below.
- 8 × Neon tetra
- 6 × Corydoras catfish
Hardy starter mix
Tough, active fish that forgive beginner mistakes.
- 3 × Platy
- 6 × Zebra danio
Gourami centerpiece
One showpiece fish with a red school.
- 1 × Honey gourami
- 6 × Cherry barb
- 3 × Amano shrimp
Shopping list for a 20-gallon tank
Sized for the “Classic community” idea above. Change the fish in the builder and the list updates.
20-gallon tank
- These fit a 20-gallon tank and get along. Aim for about 76°F.
Equipment, sized for this tank
Starter supplies
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Fish that fit a 20-gallon tank
The most of each you could keep if it were the only species in the tank.
| Fish | Kept alone, up to | Group size | Temperature |
|---|---|---|---|
| Betta | 1 | One per tank | 76–82°F |
| Neon tetra | 18 | 6 or more | 70–79°F |
| Cardinal tetra | 18 | 6 or more | 75–82°F |
| Ember tetra | 40 | 6 or more | 73–82°F |
| Rummy-nose tetra | 13 | 6 or more | 75–81°F |
| Black skirt tetra | 9 | 6 or more | 70–79°F |
| Guppy | 13 | 3 or more | 72–82°F |
| Endler's livebearer | 23 | 3 or more | 72–82°F |
| Platy | 9 | 3 or more | 70–80°F |
| Molly | 4 | 3 or more | 75–80°F |
| Zebra danio | 13 | 6 or more | 64–77°F |
| White cloud minnow | 20 | 6 or more | 60–72°F |
| Harlequin rasbora | 14 | 6 or more | 73–82°F |
| Chili rasbora | 54 | 6 or more | 72–82°F |
| Cherry barb | 12 | 6 or more | 73–81°F |
| Corydoras catfish | 12 | 6 or more | 72–79°F |
| Pygmy corydoras | 32 | 6 or more | 72–79°F |
| Otocinclus | 18 | 6 or more | 72–79°F |
| Kuhli loach | 13 | 5 or more | 75–82°F |
| Dwarf gourami | 1 | One per tank | 72–82°F |
| Honey gourami | 9 | One or more | 72–82°F |
| German blue ram | 6 | One or more | 78–85°F |
| Fancy goldfish | 1 | One or more | 60–74°F |
| Cherry shrimp | 80 | 5 or more | 65–80°F |
| Amano shrimp | 54 | 3 or more | 68–80°F |
| Nerite snail | 40 | One or more | 72–80°F |
| Mystery snail | 10 | One or more | 68–82°F |
Too big for 20 gallons: swordtail (29+ gal), tiger barb (29+ gal), bristlenose pleco (29+ gal), pearl gourami (29+ gal), angelfish (29+ gal).
20-gallon tank questions
How many fish can I put in a 20-gallon tank?
It depends on the fish. As examples, a 20-gallon tank comfortably holds 1 betta, or 18 neon tetras, or 13 guppies if kept alone. Mixed tanks hold fewer of each. The builder shows the stocking level for any combination.
What size heater does a 20-gallon tank need?
About 75 watts to hold 76°F in a 68°F room. A colder room or warmer target needs more.
What size filter does a 20-gallon tank need?
Look for a filter rated for at least 100 gallons per hour, which turns the tank over about 5 times an hour. Go higher for messy fish such as goldfish or plecos.
How much does a 20-gallon tank weigh?
About 225 pounds when filled with water, substrate and equipment. Standard dimensions are 24 × 12 × 16 inches.