125 Gallon Standard
A magnificent 6-foot aquarium. The gold standard for keeping large, active swimmers like African Cichlids, Silver Dollars, and large Loaches.
Similar Tanks & Sizes
A magnificent 6-foot aquarium. The gold standard for keeping large, active swimmers like African Cichlids, Silver Dollars, and large Loaches. With a capacity of 473 litres (125 gallons) and dimensions of 183 x 46 x 56, this long tank is compatible with 351 species in our database — giving you plenty of options for a thriving community setup.
Tank equipment picks
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Stocking Tips
- 💡With a tank this large, you have room for impressive schooling groups. Keep schooling species in groups of 8+ for the best visual impact.
- 💡Large tanks can support multiple centrepiece fish — just ensure there are enough sight-line breaks with plants and hardscape.
- 💡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
- Apistogramma Mamoré×1Centerpiece
- Chili Rasbora×6Schooling
- African Pipefish×1Bottom Dweller
Bold & Beautiful
- Arrowhead Puffer×1Centerpiece
- Dwarf Molly×6Schooling
- African Butterfly Cichlid×1Bottom Dweller
Nano-Friendly Mix
- Chili Rasbora×6Schooling
- Bladder Snail (Pest Snail)×1Bottom Dweller
Gentle Giants
- Bullseye Catfish×1Centerpiece
- Plain Silver Dollar×5Schooling
- Reedfish (Ropefish)×3Bottom Dweller
Low Maintenance Setup
- Chili Rasbora×6Schooling
- Bee Shrimp (Crystal Red / Black)×10Bottom Dweller
Schooling Showcase
- Chili Rasbora×6Schooling
- Agassiz Cory×6Bottom Dweller
Water and maintenance products
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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 Clawed Frog fits this tank now but grows rapidly — monitor closely and be prepared to upgrade.
American Grass Shrimp fits this tank now but grows rapidly — monitor closely and be prepared to upgrade.
Apple Snail fits this tank now but grows rapidly — monitor closely and be prepared to upgrade.
Arulius Barb fits this tank now but grows rapidly — monitor closely and be prepared to upgrade.
Asian Upside Down Catfish fits this tank now but grows rapidly — monitor closely and be prepared to upgrade.
Australian Smelt fits this tank now but grows rapidly — monitor closely and be prepared to upgrade.
Bala Shark needs at least 560L, which is 18% more than this tank's 473L capacity.
Banded Leporinus fits this tank now but grows rapidly — monitor closely and be prepared to upgrade.
Black Bullhead Catfish needs at least 560L, which is 18% more than this tank's 473L capacity.
Bladder Snail (Pest Snail) fits this tank now but grows rapidly — monitor closely and be prepared to upgrade.
Blue Pearl Shrimp fits this tank now but grows rapidly — monitor closely and be prepared to upgrade.
Blue Tilapia fits this tank now but grows rapidly — monitor closely and be prepared to upgrade.
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Centerpiece Fish
Bold, eye-catching species that serve as the focal point of your tank. Typically kept singly or in pairs.
Abei Puffer
Pao abei
A highly intelligent, interactive, and aggressive freshwater pufferfish native to the Mekong basin. They feature an earthy base color speckled with bright orange or pale spots. As true ambush predators and molluscivores, they require hard-shelled foods like snails and crustaceans to naturally file down their ever-growing teeth. Due to their extreme territoriality and formidable bite, they are widely considered a 'wet pet' and must be kept strictly alone.
Aequidens Jenaro Herrera
Aequidens sp. 'Jenaro Herrera'
An undescribed and beautifully colored South American cichlid hailing from the Peruvian Amazon (Rio Itaya/Ucayali drainages). Often confused in the trade with Aequidens diadema, this species features an attractive green-gold metallic sheen and reddish fins as it matures. They are relatively peaceful for mid-sized cichlids but will aggressively defend their territory during spawning and are capable predators of small fish.
Aequidens diadema (Diadem Cichlid)
Aequidens diadema
A medium-sized, semi-aggressive South American cichlid native to the slow-moving rivers and blackwater streams of the Amazon basin. Known for their striking colors and strong personalities, they are omnivorous with a carnivorous tendency. Like many cichlids, they are notorious for digging and rearranging their habitat. They do well in large community tanks with appropriately sized tank mates but are fiercely intolerant of their own kind.
Aequidens sp. Atabapo
Aequidens sp. Atabapo
A rare, undescribed species of Acara native to the blackwater Rio Atabapo in South America. They are characterized by small spots on the head and a typical robust, deep Aequidens body. Like other Acaras, they are moderately aggressive (especially when breeding) and thrive in very soft, warm, acidic water with sandy substrates and leaf litter.
Afra Cichlid
Cynotilapia afra
A highly active and aggressive Mbuna (rock-dwelling cichlid) endemic to Lake Malawi. Distinctive for their unicuspid 'dog-like' teeth, they natively feed on zooplankton in the water column but remain tied to rocky territories. They require a hard, alkaline water environment with abundant rockwork for hiding and establishing territories. Best kept in a densely stocked, carefully managed species harem or Mbuna community to disperse extreme aggression.
African Butterfly Fish
Pantodon buchholzi
A fascinating, prehistoric-looking surface dweller native to the slow-moving waters of West Africa. They are strictly top-dwelling ambush predators with a completely flat back and upturned mouth designed to hunt insects and small fish. A tight-fitting lid is absolutely mandatory as they are exceptional jumpers capable of gliding above the water.
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Schooling Fish
Active swimmers best kept in groups. They bring movement and colour to the mid and upper levels of your tank.
Ajamaru Rainbowfish
Melanotaenia ajamaruensis
A highly active, schooling rainbowfish endemic to the Ayamaru Lakes in West Papua, Indonesia. Currently listed as Critically Endangered in the wild. It is closely related to Boeseman's Rainbowfish but possesses a notably more slender body and more prominent reddish-brown horizontal striping. They thrive in hard, alkaline water with dense vegetation and require significant horizontal swimming space.
Allen's Rainbowfish
Chilatherina alleni
A rare and highly active rainbowfish native to West Papua, Indonesia (Wapoga River basin). Known as the 'Wapoga Rainbowfish', they undergo a dramatic color transformation as they mature, developing intense metallic blues, greens, and reds. As exceptionally fast, continuous swimmers, they require a 4-foot (120cm) aquarium minimum to thrive without stress.
Angfa Rainbowfish
Melanotaenia angfa
A beautiful and active schooling fish native to the Yakati River system in West Papua. Named in honor of the Australia New Guinea Fishes Association (ANGFA). Like many large rainbowfish, they are vigorous swimmers that require long aquariums to thrive. They display their best colors in well-planted tanks with clean, well-oxygenated water.
Arfak Rainbowfish
Melanotaenia arfakensis
A lively and relatively rare schooling fish endemic to the fast-flowing streams of the Bird's Head Peninsula in West Papua. Known for their energetic swimming and beautiful subtle coloration, with dominant males displaying bright orange-red fins edged in black. As active swimmers, they require long aquariums with high oxygenation and moderate to high water flow.
Australian Smelt
Retropinna semoni
A slender, silvery schooling fish native to Australia. They are pelagic and found in huge numbers in the wild across freshwater rivers, billabongs, and brackish estuaries. Known for their distinct cucumber-like odor when handled. In the aquarium, they are highly sensitive to handling and require mature, stable water with plenty of open swimming space. Best kept in single-species setups or with very peaceful, temperate tank mates.
Axelrod's Rainbowfish
Chilatherina axelrodi
A highly active, colorful schooling fish native to Papua New Guinea. Known for a bluish-grey upper body and yellowish-white lower body divided by a dark lateral stripe. Like most rainbowfish, they are incredibly fast, active swimmers that require pristine water, moderate flow, and significant horizontal swimming space.
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Bottom Dwellers
Species that inhabit the lower reaches of the aquarium, helping keep the substrate clean and adding activity to the tank floor.
Adolfo Cory
Corydoras adolfoi
Adolfo's Corydoras is a highly sought-after, peaceful schooling catfish native to the blackwater habitats of the Rio Negro basin. They are easily identified by their bright orange nape and distinct black eye stripe. Like all corydoras, they require soft sand substrate to protect their delicate sensory barbels as they constantly sift the bottom for food.
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.
African Dwarf Frog
Hymenochirus boettgeri
A fully aquatic amphibian that is peaceful and highly entertaining. They possess lungs and must regularly dart to the surface to breathe air, so tank height should ideally be under 40cm (15 inches). Due to their poor eyesight, they hunt by smell and tactile vibration, making them slow feeders that can easily starve if housed with fast, aggressive fish. They are social creatures that thrive in small groups.
African Pipefish
Enneacampus ansorgii
The African Pipefish is a fascinating, needle-thin relative of the seahorse native to West African streams. They are considered an expert-level oddball because they are very weak swimmers and almost exclusively require tiny live foods (like baby brine shrimp, daphnia, or micro-fauna). They are highly peaceful but will easily starve if housed with fast-moving community fish that outcompete them for food.
Agassiz Cory
Corydoras agassizii
A peaceful, bottom-dwelling armored catfish native to the Amazon River basin. They are easily identified by their silvery body with dark spots and a distinct black mask over their eyes. Like all Corydoras, they are highly social and must be kept in groups. A soft sand substrate is absolutely essential to protect their delicate sensory barbels as they forage.
Alligator Pleco
Pterygoplichthys scrophus
The Alligator or Rhino Pleco is a large, heavily armored catfish easily identified by the prominent ridge along its back and its flared nasal passages. While an excellent algae eater and scavenger, it grows massive and produces an extreme amount of waste. It requires driftwood for grazing and digestion.
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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.
Balloon Molly
Poecilia latipinna hybrid
A selectively bred morphological variant characterized by a shortened spine and a rounded, balloon-like belly. Due to their altered anatomy, they are poorer swimmers than standard mollies and are prone to digestive and swim bladder issues. Like all mollies, they thrive in hard, alkaline water, appreciate algae in their diet, and are highly tolerant of brackish conditions.
Betta Imbellis
Betta imbellis
Known as the 'Peaceful Betta', Betta imbellis is a wild species closely related to Betta splendens. Unlike their highly aggressive domestic cousins, they can often be kept in pairs or carefully managed groups. They are native to blackwater swamps and require calm, tannin-stained water with plenty of cover. They are exceptionally prone to jumping.
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.
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Frequently Asked Questions — 125 Gallon Standard
How many fish can I put in a 125 Gallon Standard?
The 125 Gallon Standard (473 L / 125 gal) is compatible with 351 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 125 Gallon Standard?
Popular centrepiece options for this tank include Abei Puffer, Aequidens Jenaro Herrera, Aequidens diadema (Diadem Cichlid). 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 125 Gallon Standard?
Great schooling options include Ajamaru Rainbowfish, Allen's Rainbowfish, Angfa Rainbowfish. Schooling fish should be kept in groups of at least 6 to encourage natural behaviour and reduce stress.
What bottom dwellers suit a 125 Gallon Standard?
Suitable bottom dwellers include Adolfo Cory, African Butterfly Cichlid, African Dwarf Frog. 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 125 Gallon Standard 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.