How many fish in a 40 gallon tank?
The 40 gallon breeder has a wide footprint, great for bottom dwellers and aquascaping.
A 40 gallon tank (151 L) can hold roughly 66 small fish like neon tetras on their own, or a smaller mixed community. Big fish count for much more than small ones, so plan by adult size and waste, not inches per gallon.
40 gallon stocking ideas
Each plan is checked by our calculator for space, water and compatibility. Add fish gradually to a cycled tank.
Ram and tetra tank
- 2 × German blue rams
- 12 × Cardinal tetras
- 6 × Sterbai corydoras
Rams need warm, stable, very clean water.
Two fancy goldfish
- 2 × Fancy goldfish
No heater needed. Goldfish need strong filtration and big water changes.
Equipment for a 40 gallon tank
Sized for a 40 gallon tank (36 × 18 × 16 in) with tropical community fish. Your fish may need extras: the stocking calculator builds a list for your exact plan.
- 40 gallon aquarium (tank or kit) (opens Amazon in a new tab)Bigger tanks are more stable and easier for beginners. How to choose
- Aquarium stand for 40 gallons (opens Amazon in a new tab)The water alone weighs about 334 lb (151 kg), before glass, gravel and rock. How to choose
- Adjustable heater, 150 W (opens Amazon in a new tab)Holds about 78 °F (25.5 °C) in a room at 65 °F (18 °C). How to choose
- Aquarium thermometer (opens Amazon in a new tab)Check it daily: heaters can fail stuck on or off. How to choose
- Hang-on-back filter rated 160–240 GPH (opens Amazon in a new tab)Community tank: 4–6 times the tank volume per hour. How to choose
- About 75 lb of aquarium gravel (opens Amazon in a new tab)Enough for a layer about 2 in (5 cm) deep. Smooth gravel suits most community fish. How to choose
- Water conditioner (dechlorinator) (opens Amazon in a new tab)Removes chlorine and chloramine from tap water. Seachem Prime is a popular, concentrated choice. How to choose
- Liquid test kit (ammonia, nitrite, nitrate, pH) (opens Amazon in a new tab)Liquid kits are more accurate than strips. The API Freshwater Master Test Kit is the common choice. How to choose
- Gravel vacuum (siphon) (opens Amazon in a new tab)Cleans the gravel and does the water change in one go. How to choose
- LED aquarium light, about 36 in long (opens Amazon in a new tab)Match the light to the tank length. Basic LEDs grow easy plants. How to choose
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Fish that suit a 40 gallon tank
The number is the most you could keep of that species alone, by bioload. Mix species and you'll need fewer of each.
| Species | Adult size | Keep |
|---|---|---|
| Angelfish | 15 cm (5.9 in) | 1 male |
| Betta fish | 6.5 cm (2.6 in) | 1 male |
| Bristlenose pleco | 12 cm (4.7 in) | 1 male |
| Bronze corydoras | 7 cm (2.8 in) | 6–23 |
| Dwarf gourami | 7.5 cm (3 in) | 1 male |
| Fancy goldfish | 15 cm (5.9 in) | 1–3 |
| Guppy | 5 cm (2 in) | 3–39 |
| Neon tetra | 3.5 cm (1.4 in) | 8–66 |
| Panda corydoras | 4.5 cm (1.8 in) | 6–45 |
| Tiger barb | 7 cm (2.8 in) | 8–19 |
| Zebra danio | 5 cm (2 in) | 6–39 |
| Black skirt tetra | 6 cm (2.4 in) | 8–26 |
| Cardinal tetra | 4 cm (1.6 in) | 8–54 |
| Celestial pearl danio | 2.5 cm (1 in) | 8–110 |
| Cherry barb | 5 cm (2 in) | 6–39 |
| Chili rasbora | 2 cm (0.8 in) | 10–154 |
| Convict cichlid | 12 cm (4.7 in) | 1 or a pair |
| Dwarf neon rainbowfish | 6 cm (2.4 in) | 6–29 |
| Electric blue acara | 15 cm (5.9 in) | 1 or a pair |
| Ember tetra | 2 cm (0.8 in) | 8–154 |
| German blue ram | 6 cm (2.4 in) | 1 or a pair |
| Glowlight tetra | 4 cm (1.6 in) | 6–54 |
| Harlequin rasbora | 4.5 cm (1.8 in) | 8–45 |
| Hillstream loach | 6.5 cm (2.6 in) | 3–26 |
| Honey gourami | 5 cm (2 in) | 1 male |
| Julii corydoras | 5.5 cm (2.2 in) | 6–33 |
| Kribensis | 10 cm (3.9 in) | 1 or a pair |
| Kuhli loach | 9 cm (3.5 in) | 6–26 |
| Molly | 10 cm (3.9 in) | 3–11 (few males) |
| Otocinclus | 4 cm (1.6 in) | 6–54 |
| Pea puffer | 2.5 cm (1 in) | 1 male + 2 or more females |
| Pearl gourami | 11.5 cm (4.5 in) | 1 male + 2 or more females |
| Peppered corydoras | 6.5 cm (2.6 in) | 6–26 |
| Platy | 6 cm (2.4 in) | 3–29 |
| Pygmy corydoras | 2.5 cm (1 in) | 10–110 |
| Rummy-nose tetra | 5 cm (2 in) | 10–39 |
| Sterbai corydoras | 6.5 cm (2.6 in) | 6–26 |
| Three spot gourami | 12 cm (4.7 in) | 1 male |
| White cloud mountain minnow | 4 cm (1.6 in) | 6–54 |
| X-ray tetra | 4.5 cm (1.8 in) | 6–45 |
| African butterfly fish | 11 cm (4.3 in) | 1 male |
| Agassiz's dwarf cichlid | 7 cm (2.8 in) | 1 male + 2 or more females |
| Black neon tetra | 4 cm (1.6 in) | 8–54 |
| Black phantom tetra | 4 cm (1.6 in) | 6–54 |
| Bleeding heart tetra | 6.5 cm (2.6 in) | 8–23 |
| Bloodfin tetra | 5 cm (2 in) | 6–39 |
| Bolivian ram | 8 cm (3.1 in) | 1 or a pair |
| Buenos Aires tetra | 7 cm (2.8 in) | 8–19 |
| Bumblebee catfish | 7.5 cm (3 in) | 1–17 |
| Clown killifish | 3.5 cm (1.4 in) | 6–66 |
| Clown pleco | 9 cm (3.5 in) | 1 male |
| Cockatoo cichlid | 7.5 cm (3 in) | 1 male + 2 or more females |
| Diamond tetra | 6 cm (2.4 in) | 6–26 |
| Dwarf chain loach | 6 cm (2.4 in) | 6–29 |
| Emperor tetra | 5 cm (2 in) | 6–39 |
| Endler's livebearer | 3 cm (1.2 in) | 3–83 |
| Forktail blue-eye | 5 cm (2 in) | 8–39 |
| Gardneri killifish | 6 cm (2.4 in) | 1 male + 2 or more females |
| Glass catfish | 7 cm (2.8 in) | 6–23 |
| Gold barb | 7 cm (2.8 in) | 6–19 |
| Golden wonder killifish | 9 cm (3.5 in) | 1 male + 2 or more females |
| Head and tail light tetra | 4.5 cm (1.8 in) | 6–45 |
| Kubotai rasbora | 2 cm (0.8 in) | 10–154 |
| Lambchop rasbora | 3.5 cm (1.4 in) | 8–66 |
| Lemon tetra | 4.5 cm (1.8 in) | 8–45 |
| Marbled hatchetfish | 3.5 cm (1.4 in) | 8–66 |
| Odessa barb | 6 cm (2.4 in) | 6–26 |
| Panda garra | 8.5 cm (3.3 in) | 3–17 |
| Paradise fish | 8 cm (3.1 in) | 1 male |
| Peacock gudgeon | 6 cm (2.4 in) | 2–29 (few males) |
| Penguin tetra | 5 cm (2 in) | 6–39 |
| Rosy loach | 2.5 cm (1 in) | 8–110 |
| Rosy tetra | 4 cm (1.6 in) | 6–54 |
| Scarlet badis | 2 cm (0.8 in) | 1 male + 2 or more females |
| Serpae tetra | 4.5 cm (1.8 in) | 10–45 |
| Shell dweller cichlid | 4 cm (1.6 in) | 2–54 (few males) |
| Sparkling gourami | 3.8 cm (1.5 in) | 2–49 |
| Swordtail | 12 cm (4.7 in) | 4–10 (few males) |
| Threadfin rainbowfish | 4 cm (1.6 in) | 6–54 |
| Upside-down catfish | 9.5 cm (3.7 in) | 4–12 |
| Zebra pleco | 8 cm (3.1 in) | 1 male |
| Black ruby barb | 6 cm (2.4 in) | 6–26 |
| Checkerboard barb | 5 cm (2 in) | 6–39 |
| Dwarf rasbora | 2.5 cm (1 in) | 10–110 |
| Flame tetra | 3 cm (1.2 in) | 8–83 |
| Glowlight danio | 3.5 cm (1.4 in) | 6–66 |
| Green neon tetra | 2.5 cm (1 in) | 10–110 |
| Keyhole cichlid | 10 cm (3.9 in) | 2–10 |
| Least killifish | 2.5 cm (1 in) | 6–110 |
| Moonlight gourami | 14 cm (5.5 in) | 1 male |
| Pearl danio | 6 cm (2.4 in) | 6–29 |
| Silvertip tetra | 4.5 cm (1.8 in) | 8–45 |
| Thick-lipped gourami | 9 cm (3.5 in) | 1 male |
| Variatus platy | 6 cm (2.4 in) | 3–29 |
Shrimp, snails and other invertebrates
Cherry shrimp, Nerite snail, African dwarf frog, Amano shrimp, Assassin snail, Ghost shrimp, Malaysian trumpet snail, Mystery snail, Ramshorn snail, Bamboo shrimp, Crystal red shrimp, Dwarf orange crayfish, Rabbit snail, Thai micro crab, Vampire shrimp.
Fish that need a bigger tank
- Common goldfish: at least 75 gallons (284 L)
- Common pleco: at least 150 gallons (568 L)
- Oscar: at least 75 gallons (284 L)
- Bala shark: at least 230 gallons (871 L)
- Blood parrot cichlid: at least 55 gallons (208 L)
- Chinese algae eater: at least 80 gallons (303 L)
- Clown loach: at least 180 gallons (681 L)
- Denison barb: at least 75 gallons (284 L)
- Discus: at least 75 gallons (284 L)
- Dojo loach: at least 75 gallons (284 L)
Frequently asked questions
How many fish can go in a 40 gallon tank?
A 40 gallon tank (151 L) can hold roughly 66 small fish like neon tetras on their own, or a smaller mixed community. Big fish count for much more than small ones, so plan by adult size and waste, not inches per gallon.
What are the best fish for a 40 gallon tank?
Good choices include angelfish, betta fish, bristlenose pleco, bronze corydoras, dwarf gourami and fancy goldfish. Pick one centerpiece or one school plus a few bottom dwellers, then check the mix in our stocking calculator.
How big is a 40 gallon tank?
A standard 40 gallon tank is about 36 × 18 × 16 inches (91 × 46 × 41 cm). Full of water it weighs at least 334 lb (152 kg) before glass, gravel and decor.
What fish should not go in a 40 gallon tank?
Common goldfish, common plecos, oscars, bala sharks and blood parrot cichlids need more room. For example, common goldfish need at least 75 gallons (284 L).
What size heater do I need for a 40 gallon tank?
About 150 W keeps a 40 gallon tank at 78 °F (25.5 °C) in a room at 65 °F (18 °C). Use a bigger heater for a colder room, or check yours with our heater size calculator.
What size filter do I need for a 40 gallon tank?
Choose a filter rated about 160–240 gallons per hour (GPH), which is 4–6 times the tank volume for a typical community tank. Messy fish like goldfish need more; bettas need gentle flow.