20 Gallon Long
The ultimate beginner tank. The extended 30-inch length provides vital swimming space for schooling fish and a large footprint for bottom-dwelling Corydoras.
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The ultimate beginner tank. The extended 30-inch length provides vital swimming space for schooling fish and a large footprint for bottom-dwelling Corydoras. With a capacity of 76 litres (20 gallons) and dimensions of 76 x 30 x 30, this long tank is compatible with 91 species in our database — giving you plenty of options for a thriving community setup.
Stocking Tips
- 💡Larger tanks are more forgiving, but always add fish gradually — introduce 2–3 species at a time to let the biological filter adapt.
- 💡Mix species from different swim zones (top, middle, bottom) to make use of the full water column.
- 💡Long tanks provide extra swimming length, which is ideal for active mid-water swimmers and territorial species that need space.
Stocking Recipes
Pre-built species combinations that work well together in this tank.
Peaceful Community
- Black Skirt Tetra×1Centerpiece
- Chili Rasbora×6Schooling
- Bee Shrimp (Crystal Red / Black)×10Bottom Dweller
Bold & Beautiful
- Dwarf Pea Puffer×1Centerpiece
- Clown Killifish×4Schooling
- Rachov's Killifish (Annual)×1Bottom Dweller
Nano-Friendly Mix
- Chili Rasbora×6Schooling
- Bladder Snail (Pest Snail)×1Bottom Dweller
Low Maintenance Setup
- Chili Rasbora×6Schooling
- Thai Micro Crab×3Bottom Dweller
Schooling Showcase
- Chili Rasbora×6Schooling
- Cherry Shrimp×6Bottom Dweller
Colorful Community
- Zebra Danio×6Schooling
- Neon Blue Goby×3Bottom Dweller
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Commonly Mis-Stocked
These fish are frequently added to this tank but may outgrow it or cause problems. Proceed with caution.
African Jewel Cichlid requires at least 90cm of swimming length, which is 18% longer than this tank's 76cm.
Apple Snail requires at least 90cm of swimming length, which is 18% longer than this tank's 76cm.
Bladder Snail (Pest Snail) fits this tank now but grows rapidly — monitor closely and be prepared to upgrade.
Cherry Shrimp fits this tank now but grows rapidly — monitor closely and be prepared to upgrade.
Congo Tetra requires at least 90cm of swimming length, which is 18% longer than this tank's 76cm.
Empire Gudgeon requires at least 90cm of swimming length, which is 18% longer than this tank's 76cm.
Endler's Livebearer fits this tank now but grows rapidly — monitor closely and be prepared to upgrade.
Firemouth Cichlid requires at least 90cm of swimming length, which is 18% longer than this tank's 76cm.
Forktail Blue-eye fits this tank now but grows rapidly — monitor closely and be prepared to upgrade.
Freshwater Angelfish requires at least 90cm of swimming length, which is 18% longer than this tank's 76cm.
Gardner's Killifish fits this tank now but grows rapidly — monitor closely and be prepared to upgrade.
Ghost Shrimp fits this tank now but grows rapidly — monitor closely and be prepared to upgrade.
Show 20 more warnings
Centerpiece Fish
Bold, eye-catching species that serve as the focal point of your tank. Typically kept singly or in pairs.
Agassiz's Dwarf Cichlid
Apistogramma agassizii
A stunning South American dwarf cichlid known for its distinct spade-shaped tail and brilliant color morphs. They are bottom-dwelling micro-predators that sift sand for food. While generally peaceful in community tanks, they are highly territorial when breeding. They thrive in soft, acidic blackwater conditions.
Betta (Siamese Fighting Fish)
Betta splendens
The Siamese Fighting Fish is an aquarium icon known for its labyrinth organ (allowing air breathing) and vivid colors. While hardy, they require heated, filtered water (24-30°C). Males are solitary and fiercely territorial. Females are generally less ornate but can be kept in 'sororities' with strict precautions (minimum 5 females in 75L+).
Black Skirt Tetra
Gymnocorymbus ternetzi
A very hardy, deep-bodied schooling tetra native to South America. They are incredibly popular for beginners but have a reputation as fin-nippers if kept in too small a group. A proper school disperses their internal bickering and largely prevents them from harassing other tank mates.
Bolivian Ram
Mikrogeophagus altispinosus
A hardy and relatively peaceful dwarf cichlid native to the Amazon river basin. Compared to the popular German Blue Ram, the Bolivian Ram is larger, much more forgiving of water parameters, and prefers slightly cooler temperatures. They are eartheaters (geophagine) that sift through the substrate for food, making soft sand an absolute requirement to prevent gill damage.
Bumblebee Goby (Brackish)
Brachygobius xanthozonus
A miniature, bottom-dwelling goby famous for its striking black and yellow stripes. While they are often sold as freshwater fish and can survive in it temporarily, they are highly susceptible to fungal infections in fresh water and truly require a brackish setup (SG 1.002-1.005) to thrive long-term. They are notoriously picky eaters, often ignoring flakes in favor of live or frozen foods (like bloodworms or brine shrimp).
Cockatoo Dwarf Cichlid
Apistogramma cacatuoides
A highly popular and vibrant dwarf cichlid native to the Amazon basin. Named for the male's flamboyant, crest-like dorsal fin. They are cave-spawners that require a fine sand substrate (which they sift through their gills) and plenty of hiding spots. While generally peaceful in community tanks, they become fiercely territorial when breeding.
Show 17 more centerpiece fish
Schooling Fish
Active swimmers best kept in groups. They bring movement and colour to the mid and upper levels of your tank.
Beckford's Pencilfish
Nannostomus beckfordi
A peaceful, slender schooling fish native to the sluggish rivers and swamps of South America. They are famous for the males' harmless but spectacular lateral sparring displays. They require heavily planted aquariums with gentle flow and make excellent tank mates for other peaceful, soft-water species. A tight-fitting lid is essential as they are known to be proficient jumpers.
Black Neon Tetra
Hyphessobrycon herbertaxelrodi
A peaceful, active schooling fish native to the Paraguay basin. Known for its striking contrast of a dark black lateral stripe underneath a glowing iridescent white/green-gold stripe. Excellent for community aquariums, particularly in planted setups or blackwater biotope tanks with subdued lighting.
Cardinal Tetra
Paracheirodon axelrodi
A stunning schooling fish native to the upper Orinoco and Rio Negro basins in South America. Famous for its brilliant iridescent blue line and a vivid red stripe that extends the full length of its body (distinguishing it from the Neon Tetra). They are strictly schooling fish that thrive in warm, acidic blackwater environments.
Celebes Rainbowfish
Marosatherina ladigesi
An active, schooling fish native to the karst (limestone) streams of Sulawesi, Indonesia. Known for their striking neon blue lateral stripes and yellowish fins. They strictly require hard, alkaline water to thrive and are highly sensitive to soft, acidic conditions. A peaceful species that requires plenty of open swimming space.
Chili Rasbora
Boraras brigittae
A striking, deeply red nano fish native to the blackwater streams and peat swamps of southern Borneo. They are extremely peaceful and require a mature, densely planted aquarium with soft, acidic water. Due to their tiny size, they are completely safe with adult dwarf shrimp and are ideal for nano setups.
Clown Killifish
Epiplatys annulatus
A striking nano killifish resembling a tiny rocket. Native to West African swamps, they have distinct black and yellow vertical bands. They are strictly surface dwellers (top-level) and are non-annual, meaning they live longer than annual killifish (2-3+ years). They are notorious jumpers and require a tight lid.
Show 17 more schooling fish
Bottom Dwellers
Species that inhabit the lower reaches of the aquarium, helping keep the substrate clean and adding activity to the tank floor.
African Butterfly Cichlid
Anomalochromis thomasi
A peaceful, colorful dwarf cichlid from West Africa. Unlike many cichlids, it is plant-safe and generally suitable for community tanks. It is famous in the hobby as an efficient biological control for pest snails.
Amano Shrimp
Caridina multidentata
A highly popular, industrious freshwater shrimp renowned for its unmatched algae-eating abilities. Popularized by aquascaper Takashi Amano, they are significantly larger and hardier than most dwarf shrimp (like Cherry Shrimp). They are notorious food-thieves during feeding time and excellent escape artists, requiring a tight-fitting lid. Their larvae require saltwater to develop, so they will not overpopulate in a freshwater aquarium.
Assassin Snail
Clea helena
A highly effective and popular carnivorous freshwater snail used primarily for pest snail control. They actively hunt and consume smaller snails like bladder, ramshorn, and pond snails. Featuring a striking yellow and dark brown spiraled shell, they are a functional and attractive addition to aquariums. Unlike many aquatic snails, they are not hermaphroditic and reproduce quite slowly.
Bamboo Shrimp
Atyopsis moluccensis
A large, completely peaceful freshwater filter-feeding shrimp. They use specialized fan-like appendages to catch microorganisms and fine food particles from the water column. They require an established aquarium with moderate to high water flow and tall resting places (like driftwood) directly in the current.
Bee Shrimp (Crystal Red / Black)
Caridina cantonensis
A sensitive, highly prized dwarf shrimp species known for its vivid red/white or black/white banding. Unlike the hardy Cherry Shrimp (Neocaridina), Bee Shrimp require cool, soft, acidic water and typically require active buffering soil to thrive. They are peaceful grazers perfect for specific biotope setups.
Bladder Snail (Pest Snail)
Physella acuta
A tiny, fast-moving freshwater snail almost universally introduced accidentally via live aquarium plants. While frequently labeled a 'pest' due to their rapid, prolific reproduction, they are actually an excellent cleanup crew. They consume algae, uneaten food, and decaying plant matter without harming healthy plants. They are hermaphroditic and can self-fertilize, meaning a single snail can start a massive colony.
Show 33 more bottom dwellers
Other Compatible Species
Additional species that are compatible with this tank size but don't fall neatly into the categories above.
Amazon Leaf Fish
Monocirrhus polyacanthus
A master of camouflage that perfectly mimics a dead leaf drifting in the water. This species is an extreme ambush predator with a protruding jaw that can swallow prey up to 75% of its own size. It is a 'specialist' species because nearly all specimens require live food (small fish/shrimp) and refuse dry or frozen foods. Requires acidic, blackwater conditions and zero flow.
Endler's Livebearer
Poecilia wingei
A tiny, vibrant, and highly active livebearer closely related to the Guppy. Males display intense, neon colors and patterns, while females are larger and plainly colored. They are prolific breeders and require hard, alkaline water to thrive.
Guppy
Poecilia reticulata
One of the most iconic and widely kept aquarium fish. Renowned for their incredible colors, hardiness, and prolific breeding. As livebearers, they give birth to fully formed, free-swimming fry. Males constantly pursue females for mating; therefore, a ratio of at least 2 females per male is strongly recommended to disperse stress.
Honey Gourami
Trichogaster chuna
The smallest and most peaceful member of the Trichogaster genus. Ideally suited for planted nano aquariums. Unlike the aggressive Dwarf Gourami (*T. lalius*), Honey Gouramis are timid and gentle. True Honey Gouramis rarely exceed 5cm. Note: Many bright red fish sold as 'Red Honey' or 'Red Robin' are actually Thick-lipped Gouramis (*T. labiosa*), which grow larger.
Molly (Sailfin/Black/Dalmatian)
Poecilia sphenops
Mollies are active, hardy livebearers native to the Americas. They are famous for their ability to adapt to fresh, brackish, and even full marine water. They are voracious eaters (including algae) and produce a high bioload for their size. Note: 'Molly' covers several species; the Short-finned (*P. sphenops*) and the much larger Sailfin (*P. latipinna* and *P. velifera*).
Platy
Xiphophorus maculatus
A quintessential community fish known for its durability and massive variety of colors. Native to Central America, Platies are livebearers, meaning they give birth to free-swimming fry. They are peaceful, active grazers that require hard, alkaline water to thrive. They are excellent for beginners but breed prolifically.
Frequently Asked Questions — 20 Gallon Long
How many fish can I put in a 20 Gallon Long?
The 20 Gallon Long (76 L / 20 gal) is compatible with 91 species in our database. The actual number of individual fish depends on the species mix — use the stocking recipes above as a starting point and aim to keep the total bioload below 85% of capacity.
What is the best centrepiece fish for a 20 Gallon Long?
Popular centrepiece options for this tank include Agassiz's Dwarf Cichlid, Betta (Siamese Fighting Fish), Black Skirt Tetra. A centrepiece fish should be the focal point of your aquarium — choose one with colours and behaviour that complement your other species.
What schooling fish work in a 20 Gallon Long?
Great schooling options include Beckford's Pencilfish, Black Neon Tetra, Cardinal Tetra. Schooling fish should be kept in groups of at least 6 to encourage natural behaviour and reduce stress.
What bottom dwellers suit a 20 Gallon Long?
Suitable bottom dwellers include African Butterfly Cichlid, Amano Shrimp, Assassin Snail. These species occupy the lower zone of your tank, helping to keep the substrate tidy and adding activity to an often-overlooked area.
What temperature should a 20 Gallon Long be?
The ideal temperature depends on the species you keep. Most tropical freshwater fish thrive between 24–27°C (75–80°F). Check each species' requirements and aim for the overlapping range that suits all your inhabitants.