🐟 Did you know?
Freshwater fun facts
201 genuinely delightful things about the fish and invertebrates we cover — from a betta dad who catches his eggs in his mouth to a zebrafish that can regrow its own heart. Because this is Finfern, every fact is checked against a named source and the popular-but-false trivia (yes, the goldfish “3-second memory”) is left out — real wonder, no myths.
Jump to a species, or just scroll and enjoy.
Betta
- Bettas are labyrinth fishes: they gulp air at the surface and can survive in still, oxygen-poor waters like rice paddies and roadside ditches. SeriouslyFish
- The male is a devoted father who builds a floating bubble-nest, catches falling eggs in his mouth, and alone guards and tends the brood. SeriouslyFish
- The name “betta” comes from ikan betah, the Malay word for these fish, while splendens is Latin for “shining, glittering”. SeriouslyFish
Honey Gourami
- A courting male transforms, his body glowing bright orange while his head and underside turn deep blue-black to woo a mate. SeriouslyFish
- The genus name Trichogaster means “hair-belly” in Greek, a nod to the thread-like pelvic fins these gouramis use like feelers. SeriouslyFish
- Unusually, the male's bubble-nest contains no plant material and is often built beneath a broad leaf or in a tank corner. SeriouslyFish
Dwarf Gourami
- The male reinforces his floating bubble-nest with tiny pieces of plant material — an amazing feat of construction to watch. SeriouslyFish
- Courtship flips the script: once the nest is done the female takes charge, nudging the male beneath it with her snout. SeriouslyFish
- A single brood can number up to 700 eggs, all tended by the male in his bubble-nest. SeriouslyFish
Pearl Gourami
- A male in full breeding dress, flushed with orange-red across the throat, is one of the most stunning fish in the hobby. SeriouslyFish
- This bubble-nesting builder can craft a floating nest up to 10 inches across among the surface plants. SeriouslyFish
- A hardy and long-lived fish, the pearl gourami may live for eight years or more in the aquarium. SeriouslyFish
Guppy
- Guppies are livebearers, giving birth to fully-formed swimming young rather than laying eggs — from 5 to 100 at a time. SeriouslyFish
- A female can store viable sperm for months, still producing broods for half a year or more with no male present. SeriouslyFish
- Voracious mosquito-larvae eaters, guppies have been introduced around the world as a means of malaria control. SeriouslyFish
Endler's Livebearer
- First found in 1937, Endler's livebearer was rediscovered by John Endler in 1975 in a lagoon in northeastern Venezuela. SeriouslyFish
- These prolific livebearers can produce a fresh brood roughly every 23 to 24 days. SeriouslyFish
- Young Endlers grow up fast — males show full adult colour in just 3 to 5 weeks, and females breed by two months old. SeriouslyFish
Platy
- Platies are peaceful livebearers, giving birth to broods of up to 80 fully-formed fry after four to six weeks. SeriouslyFish
- The genus Xiphophorus means “sword-bearing” in Greek; maculatus is Latin for “spotted”, after the platy's belly spot. SeriouslyFish
- Famous varieties like the mickey mouse, wagtail and comet platy come from selective breeding, some crossed with swordtails. SeriouslyFish
Molly
- Mollies are livebearers that carry their young internally, and a single female can drop a brood of up to 120 free-swimming fry. SeriouslyFish
- So salt-tolerant it can be acclimated to full marine conditions, the molly is even used to help cycle new saltwater aquariums. SeriouslyFish
- Its genus name Poecilia is from the Greek for “variegated”, fitting a fish bred into gold, silver, dalmatian, lyretail and the famous black morph. SeriouslyFish
Swordtail
- The name Xiphophorus means “sword-bearer” in Greek, for the long blade-like extension trailing from the lower tail lobe of adult males. SeriouslyFish
- A female swordtail can store a male's sperm for months, letting her keep producing broods long after mating. SeriouslyFish
- Swordtails are prized in science, including biomedical research into the genetics and causes of cancer. SeriouslyFish
Neon Tetra
- Some wild neon tetras carry extra golden scales caused by a parasite that triggers guanine deposits, and are sold as “platinum” or “gold” neons. SeriouslyFish
- The neon tetra was named for aquarist and publisher William T. Innes, and was first described from an aquarium import rather than a wild-caught fish. SeriouslyFish
- Neon tetra eggs and fry are so light-sensitive that breeders keep the spawning tank in near-darkness during their first days of life. SeriouslyFish
Cardinal Tetra
- In the wild the cardinal tetra is almost an annual fish — individuals over a year old are rarely found — though it lives far longer in aquaria. SeriouslyFish
- Many cardinal tetras are still wild-caught via Project Piaba on the rio Negro, where the fish makes up as much as 60% of yearly income in the town of Barcelos. SeriouslyFish
- It was almost named Hyphessobrycon cardinalis, but a rival description published first named it for Tropical Fish Hobbyist founder Dr. Herbert R. Axelrod. SeriouslyFish
Ember Tetra
- The ember tetra is a true miniature, reaching only about 20 mm (under an inch) in standard length. SeriouslyFish
- It hails from Brazil's Rio das Mortes, the “River of the Dead”, a tributary of the Araguaia in the Amazon basin. SeriouslyFish
- In nature the ember tetra is a micropredator, hunting tiny invertebrates and other zooplankton. SeriouslyFish
Harlequin Rasbora
- Unlike most small cyprinids that scatter eggs, harlequins spawn upside-down, gluing their eggs to the underside of a broad plant leaf. SeriouslyFish
- The harlequin was first exported for the hobby in the early 1900s, making it one of the trade's most enduring species. SeriouslyFish
- Its trademark black “wedge” can be sexed by shape: sharp and well-defined in males, but softly rounded in females. SeriouslyFish
Rummynose Tetra
- The name rhodostomus is Greek for “red mouth”, for the fish's glowing red nose and face. SeriouslyFish
- The red “blush” is a health tell: the rummynose loses its colour in unfavourable or alkaline water, so a faded nose signals poor conditions. SeriouslyFish
- It is one of the most tightly shoaling small tetras — so much so it does poorly unless kept in groups of ten or more. SeriouslyFish
Corydoras Catfish
- The bronze cory can breathe air: it gulps oxygen at the surface and absorbs it through its gut, surviving water so low in oxygen it would suffocate most fish. Wikipedia
- During its “T-position” courtship the female drinks the male's sperm, which passes through her gut and is released with her eggs into a pouch made by her pelvic fins. Wikipedia
- The name Corydoras comes from the Greek for “helmet” and “skin”, a nod to the two rows of overlapping bony plates that armour the fish's flanks. SeriouslyFish
Bristlenose Pleco
- Only male bristlenose plecos grow the branching “bristles” on the snout that give the fish its name; females have a bare snout. SeriouslyFish
- Bristlenose plecos are cave-spawners in which the father alone guards the eggs and fry, fanning and defending the brood inside his chosen cavity. SeriouslyFish
- The genus name Ancistrus means “fish hook”, for the hooked odontodes (spiny skin-teeth) that males can flare out from the gill covers. SeriouslyFish
Otocinclus
- Otocinclus can breathe air, sometimes darting to the surface for a gulp; a modified section of their oesophagus works in aerial respiration and adds buoyancy. SeriouslyFish
- The name Otocinclus, from the Greek for “ear” and “grid”, refers to a perforated grid-like patch of bone behind the eye of these tiny suckermouth catfish. SeriouslyFish
- In the wild otos graze almost constantly on algae and microbes, needing so little protein that they feed near-continuously through the day. SeriouslyFish
Kuhli Loach
- The kuhli loach has an eel-shaped, snake-like body with four pairs of barbels around its mouth and eyes covered by transparent skin. Wikipedia
- Kuhli loaches carry a small erectable spine beneath each eye that they can deploy to jab would-be predators. Wikipedia
- This slender nocturnal loach is long-lived, reportedly reaching around 14 years of age. Wikipedia
Angelfish
- Angelfish are cichlids that spawn on vertical surfaces like broad leaves or slate, and bonded pairs guard both the eggs and the hatched fry. SeriouslyFish
- Despite their peaceful looks, angelfish are true cichlids and predatory enough to eat small tankmates such as tetras. SeriouslyFish
German Blue Ram
- The German blue ram is a biparental substrate spawner: male and female share brood care equally, guarding eggs and fry together. SeriouslyFish
- You can often sex a ram by the belly: most females show a pinkish or rosy patch on the abdomen that males lack. SeriouslyFish
- The genus name Mikrogeophagus means “small Geophagus”, linking this dwarf cichlid to the larger “earth-eating” South American cichlids. SeriouslyFish
Apistogramma
- In the cockatoo cichlid the female alone tends the eggs and fry, and can turn so aggressive that in small tanks the larger male may need removing. SeriouslyFish
- Male cockatoo cichlids are bigger and far more colourful than females, and grow dramatically extended, spiky dorsal rays that suggest a cockatoo's crest. SeriouslyFish
Zebra Danio
- Zebrafish were the first fish sent into space, and their transparent embryos let scientists watch development live from fertilisation onward. Wikipedia
- Zebrafish can fully regenerate their own heart — an ability the British Heart Foundation has studied for possible use in human medicine. Wikipedia
- The fluorescent GloFish sold in pet stores were originally engineered from the zebrafish, a major biomedical model animal. Wikipedia
White Cloud Mountain Minnow
- Believed extinct in the wild for over 20 years, the White Cloud Mountain minnow was later rediscovered in a new population on Hainan Island. Wikipedia
- Its genus name Tanichthys means “Tan's fish”, honouring the Boy Scout leader Tan Kam Fei credited with its 1932 discovery near Guangzhou. Wikipedia
- This hardy minnow can survive water as cold as 5°C (41°F), making it well suited to unheated aquariums and outdoor ponds. Wikipedia
Celestial Pearl Danio
- The celestial pearl danio was discovered only in 2006 and reached the aquarium trade so fast it was a hit before being formally described. Wikipedia
- It lives in a tiny high-altitude area above 1,000 m near Inle Lake in Myanmar, where its transparent gill covers let the red gills show through. Wikipedia
- First mistaken for a Microrasbora and dubbed the “galaxy rasbora”, it was later shown by genetics to be a true Danio. Wikipedia
Fancy Goldfish
- Fancy goldfish descend from a natural gold mutation of a silver carp in imperial China, selectively bred for colour over 1,000 years ago. Wikipedia
- The first fancy-tailed goldfish were recorded during China's Ming dynasty, and by 1603 goldfish had been introduced to Japan. Wikipedia
- Goldfish are tetrachromats, with four cone types sensitive to red, green, blue and ultraviolet light, so they see colours humans cannot. Wikipedia
Common Goldfish
- The “three-second memory” is a myth: a 1994 maze experiment (and MythBusters) showed goldfish remember for months, not seconds. Wikipedia
- Wild goldfish typically grow 12–22 cm but can reach 41 cm (16 in), far larger than most people picture. Wikipedia
- Goldfish use associative and social learning, and over time learn to recognise their owner and “beg” for food as they approach. Wikipedia
Cherry Shrimp
- The wild cherry shrimp is actually a mottled brown; the vivid red is a selectively bred colour morph, alongside orange, yellow, blue and more. Wikipedia
- Cherry shrimp skip a swimming larval stage entirely, hatching as roughly 1 mm copies of the adults after about three weeks. Wikipedia
- A breeding female carries a triangular egg “saddle” on her back that is green or yellow depending on her developing eggs. Wikipedia
Amano Shrimp
- Amano shrimp rarely breed in home tanks because their newly hatched larvae must drift to brackish or saltwater to develop before returning to freshwater. Wikipedia
- The shrimp is named for aquascaper Takashi Amano, who popularised it as an algae-cleaner in planted tanks in the early 1980s. Wikipedia
- Long sold to aquarists as Caridina japonica, the Amano shrimp was renamed Caridina multidentata after a 2006 study. Wikipedia
Nerite Snail
- The zebra nerite lays eggs freely in freshwater, but its larvae need brackish or saltwater to develop — so it can never overpopulate a freshwater tank. Wikipedia
- Nerite snails are prized because they graze algae in freshwater tanks yet can only actually reproduce in brackish or salt water. Wikipedia
Mystery Snail
- The mystery snail is born with both gills and a lung, plus a small siphon tube it extends to the surface to breathe air. Wikipedia
- Female mystery snails lay their egg clutches above the water line, attaching them to glass, lids or driftwood rather than underwater. Wikipedia
- Mystery snails have complex eyes on stalks that they can regenerate completely, even after an eyestalk is cut through the middle. Wikipedia
Kribensis
- In kribensis, water chemistry skews the brood's sex ratio: more alkaline water produces mostly males, more acidic water mostly females. SeriouslyFish
- Kribensis form monogamous pairs and spawn inside caves, the female often initiating by dancing and flashing her deep-purple breeding belly. SeriouslyFish
- A West African dwarf cichlid, the kribensis has been a hobby favourite since its introduction back in the 1950s. SeriouslyFish
Bolivian Ram
- The Bolivian ram is a biparental substrate spawner: both parents share brood care and shuttle their fry between pits dug in the substrate. SeriouslyFish
- The genus name Mikrogeophagus means “small Geophagus”, from the Greek for “small” plus the eartheater genus Geophagus. SeriouslyFish
- The Bolivian ram was first imported to the hobby in 1985 by Horst Linke and Wolfgang Staeck. SeriouslyFish
Panda Cory
- The panda cory is named for its panda-like markings — a dark eye-patch and body blotches recalling the giant panda. SeriouslyFish
- Like all Corydoras, the panda cory is a facultative air-breather, gulping air at the surface and absorbing oxygen through a modified, blood-rich intestine. SeriouslyFish
- When it first reached the hobby in the late 1970s the panda cory was wildly expensive and sought after; it is now mass-bred and hugely popular. SeriouslyFish
Pygmy Cory
- Unlike most bottom-hugging corydoras, the pygmy cory tends to shoal in the middle levels of the water, out in open water. SeriouslyFish
- At only about 30 mm long, the pygmy cory is small enough that angelfish, gouramis and larger catfish may treat it as a snack. SeriouslyFish
Chili Rasbora
- The tiny chili rasbora tops out around 20 mm and comes from black-water peat-swamp streams where the water can be as acidic as pH 4.0. SeriouslyFish
- Its genus name Boraras is an anagram of Rasbora, coined to reflect the reversed ratio of abdominal to caudal vertebrae in these nano fish. SeriouslyFish
- The species name brigittae honours the wife of describer E. Vogt, who named it in 1978. SeriouslyFish
Cherry Barb
- The cherry barb is endemic to Sri Lanka and listed as Vulnerable on the IUCN Red List, threatened by habitat loss and past over-collection. Wikipedia
- Its natural streams flow through Sri Lanka's rainforest “wet zone”, which receives 2,000–3,000 mm of rain a year in the south-west monsoons. SeriouslyFish
- The brightest wild cherry barbs are reportedly becoming scarcer, as selective collection for the trade may have altered wild populations. SeriouslyFish
Sparkling Gourami
- The sparkling gourami “croaks” audibly by stretching and plucking modified pectoral-fin tendons like guitar strings — a mechanism unique among labyrinth fishes. SeriouslyFish
- During courtship the female makes “purring” sounds to initiate spawning — one of very few fish known to do this. SeriouslyFish
- Rival males can settle disputes without fighting by sizing each other up through visual and acoustic “croaking” signals. SeriouslyFish
Assassin Snail
Tiger Barb
- Tiger barbs are named for the four dark vertical bars on their body — tetrazona means “four bands” in Greek. SeriouslyFish
- The tiger barb is one of the species turned into fluorescent “GloFish”, among the first genetically modified animals to become publicly available. Wikipedia
- Its reputation for fin-nipping seems to flare mainly when too few are kept together or space is limited. SeriouslyFish
Clown Loach
- Clown loaches produce audible clicking sounds that grow louder when the fish are excited, thought to come from grinding their throat teeth. SeriouslyFish
- It has sharp, motile sub-ocular spines hidden in skin pouches that erect when the fish is stressed — and can even break human skin. SeriouslyFish
- Properly cared for, clown loaches can live over twenty years, and wild spawning fish measure a hefty 12–20 cm. SeriouslyFish
Discus
- Adult discus secrete a nutritious “discus milk” through their skin, and their fry feed on this mucus for the first four weeks of life. Wikipedia
- The genus name Symphysodon, coined by Johann Jakob Heckel in 1840, refers to the unusual symphysis (joining) of the fish's teeth. Wikipedia
- Though discus reach only about 6 inches long, they can grow nearly as tall as they are long, giving their signature disc shape. SeriouslyFish
Oscar
- The eyespot on an oscar's tail is thought to mimic its head, so a foraging fish looks as if its head points up when it's actually its tail. Animal Diversity Web
- Those tail eyespots may help limit fin-nipping by piranhas, which share the oscar's natural Amazon waters. Wikipedia
- In its native South America the oscar is often sold as a food fish, and specimens have been reported up to 70 cm long and 9 kg. Wikipedia
Glowlight Tetra
- The glowlight tetra wears a single bright iridescent orange-to-red stripe running the whole length of its silver body, snout to tail. Wikipedia
- The species is known only from the Essequibo river system in Guyana, so every one in the hobby is farm-bred, never wild-caught. SeriouslyFish
Rosy Barb
- The rosy barb is native across South Asia, ranging from Pakistan through India, Nepal and Bangladesh. SeriouslyFish
- Escaped rosy barbs have established feral populations far from home, including in Singapore, Australia and Mexico. SeriouslyFish
- The genus name Pethia comes from the Sinhala (Sri Lankan) vernacular word for small cyprinids. SeriouslyFish
Common Pleco
- The Amazon sailfin catfish can reach nearly 58 cm (about 23 inches) long, far bigger than most home tanks can hold. FishBase
- It is a facultative air-breather, able to gulp atmospheric air to survive in low-oxygen water. FishBase
- A native of the Amazon basin, this catfish has been introduced to warm rivers well outside its natural range. FishBase
Ramshorn Snail
- Unlike most molluscs, ramshorn snails carry iron-based haemoglobin instead of copper-based haemocyanin, which tints their bodies reddish. Wikipedia
- Though aquatic, ramshorn snails are air-breathers with a lung-like pulmonary sac rather than gills. Animal Diversity Web
- Their flat disc-like shell is coiled in a single plane — the family name Planorbidae comes from that “planate” shape. Animal Diversity Web
Boesemani Rainbowfish
- Boesemani rainbowfish are found naturally only in the Ayamaru lakes of the remote Vogelkop Peninsula in Indonesian New Guinea. SeriouslyFish
- Despite being a hobby staple, the species is genuinely rare in the wild and listed on the IUCN Red List. SeriouslyFish
Dwarf Neon Rainbowfish
- The dwarf neon rainbowfish is endemic to the Mamberamo river system in New Guinea, one of the island's largest rivers at over 2,000 km long. SeriouslyFish
- Females attach their eggs to plants one by one on a tiny thread, spawning small batches daily over several weeks. SeriouslyFish
Yoyo Loach
- Yoyo loaches make audible clicking sounds that grow louder when the fish are excited, thought to come from grinding their throat teeth. SeriouslyFish
- Like most botiid loaches they will prey on aquatic snails, though they are not obligate snail-eaters. SeriouslyFish
- It is named for the Almora district of India; the common “Pakistani loach” label is a misnomer, as it lives in the Ganges drainage. SeriouslyFish
Dwarf Chain Loach
- Its genus name Ambastaia honours a river, Ambastai, named in the geographer Ptolemy's 2nd-century Geography and thought to be the Mekong. SeriouslyFish
- A miniature social Botia relative, it forms complex hierarchies and needs company — kept alone it turns withdrawn or aggressive. SeriouslyFish
- Nicknamed “chipmunk botia”, it nearly vanished from the hobby before 2000; today's fish are farm-bred, as wild-type breeding is almost unheard of. SeriouslyFish
Denison Barb
- Endemic to India's Western Ghats, it is listed as Endangered on the IUCN Red List, with wild stocks thought to have fallen by up to 50% in about 15 years. SeriouslyFish
- In India it is known as “Miss Kerala” and “Chorai Kanni”, literally “bleeding eyes”, for the red streak that runs back from its eye. SeriouslyFish
- During the 2000s this barb was the Indian state of Kerala's single most important aquarium export, before wild collection was restricted. SeriouslyFish
Congo Tetra
- This iridescent characin is African, endemic to the Congo River drainage in the Democratic Republic of Congo. SeriouslyFish
- Males grow larger and far more colourful, developing trailing filaments on the tail and a greatly extended dorsal fin. SeriouslyFish
- Young fish are sold as drab greyish juveniles and often overlooked, only developing their spectacular shimmer once settled and mature. SeriouslyFish
Siamese Algae Eater
- It is famed as one of the few fish that will eat tough “black brush” algae, a red alga that is otherwise very hard to remove once established. SeriouslyFish
- The name “Siamese algae-eater” actually covers several near-identical Crossocheilus species traded interchangeably, so “SAEs” aren't all one fish. SeriouslyFish
- In the wild it is an aufwuchs grazer on algae, diatoms and microbes, and copes poorly with high-protein food. SeriouslyFish
Hillstream Loach
- A sucker-bodied torrent fish, it grazes biofilm in fast headwaters and can literally climb aquarium glass, so a tight lid is essential. SeriouslyFish
- Males stage dominance duels belly-to-belly, both fish rearing their bodies off the substrate into a near-upright stance. SeriouslyFish
- It was first recorded by the naturalist Diard over 150 years before its 1990s “rediscovery”, reaching the hobby only in the mid-2000s. SeriouslyFish
Three-spot Gourami
- The blue, gold, opaline, cosby, marbled and silver gouramis are all one species — selectively bred colour forms of the wild blue-grey three-spot. SeriouslyFish
- It is a bubble-nester: the male builds a floating nest of bubbles and plant bits, then guards the eggs and fry alone after driving the female off. SeriouslyFish
- Around the central and lower Mekong, populations migrate into flooded forest in the wet season and return to the river as the water recedes. SeriouslyFish
Convict Cichlid
- A famously devoted parent: the female tends up to about 300 eggs while the male patrols the territory, and a pair will even attack an unwary finger. SeriouslyFish
- Its name comes from the Latin for “black-banded” (nigro + fasciatus), a nod to the vertical stripes that also earned it the “convict” nickname. SeriouslyFish
- Pound for pound remarkably tough, a breeding convict will take on fish several times its own size and win with ease. SeriouslyFish
Electric Yellow Lab
- The electric yellow lab is a cichlid endemic to just the central-western coast of Lake Malawi in East Africa, found nowhere else on Earth. Wikipedia
- It's a maternal mouthbrooder: the female carries the eggs in her mouth, where they hatch and develop for about three weeks. Wikipedia
- The bright yellow aquarium fish is a natural colour morph from Lion's Cove, one of many wild variants of this species. Wikipedia
Clown Pleco
- The clown pleco is a genuine wood-eater (xylivore) and needs driftwood, mirroring its wild home among submerged driftwood tangles. Wikipedia
- Native to the tannin-stained Apuré and Caroní basins of Venezuela and Colombia, it's a tiny suckermouth catfish reaching only about 8.8 cm. Wikipedia
- Its stripe pattern isn't fixed: some fish have straight bars while others show broken or wavy lines depending on their river of origin. Wikipedia
Odessa Barb
- Despite being an aquarium favourite for decades, the Odessa barb wasn't scientifically described until 2008. Wikipedia
- Its name comes from Odesa, Ukraine, where the fish first appeared in pet-enthusiast circles in the early 1970s. Wikipedia
- The species name padamya is Burmese for “ruby”, chosen for the vivid red lateral stripe of the male. Wikipedia
Pearl Danio
- The pearl danio has a genuine iridescent, pearly sheen and can appear brownish-yellow, pink or silver depending on the light. Wikipedia
- In the wild it lives along the surface of small, clear rivers and hill streams across Sumatra, Myanmar, Thailand and Vietnam. Wikipedia
- The golden pearl danios sold in shops are in reality semi-albino fish, not a separate species. Wikipedia
Weather Loach
Bamboo Shrimp
- The bamboo shrimp is a filter feeder, using feathery fan-like claspers to strain food particles from the water current. Wikipedia
- If food is scarce it switches strategy, foraging through the substrate instead of fanning the current. Wikipedia
- These Southeast Asian freshwater shrimp live on volcanic islands from Sri Lanka to Samoa and as far north as Okinawa. Wikipedia
Paradise Fish
- The paradise fish was the second Chinese ornamental fish brought to the West after the goldfish, reaching Paris in 1869. Wikipedia
- It was the first freshwater tropical fish ever successfully bred in captivity in Europe. Wikipedia
- One of few fish able to change colour in response to stimuli, a fighting male often flushes dark blue lateral lines along its sides. Wikipedia
Serpae Tetra
- The serpae tetra is notorious as a fin-nipper, but nipping eases when it's kept in a big shoal so rivals distract each other instead of tankmates. SeriouslyFish
- Its species name eques is Latin for “knight” or “horseman”; the fish is also traded as the jewel, red minor, blood or callistus tetra. SeriouslyFish
- Serpae tetras form loose hierarchies in which rival males constantly spar, and males show their best colour with rivals present. SeriouslyFish
Sterbai Cory
- Sterba's cory naturally tolerates warm water up to about 28°C (82°F), which is why it's a favourite bottom-dweller for hot discus tanks. SeriouslyFish
- Like all corys it's a facultative air-breather, gulping air at the surface and absorbing oxygen through a modified, blood-rich intestine. SeriouslyFish
- An armoured catfish, it wears two rows of bony plates instead of scales and carries sharp pectoral spines that can deliver a painful sting. SeriouslyFish
Zebra Loach
- The zebra loach's name striata is Latin for “striped”, describing the many dark bars running along its body. SeriouslyFish
- It's a social Botia native only to fast, forested hill rivers of India's Western Ghats. SeriouslyFish
- Inquisitive and prone to squeezing into crevices, these loaches are also known jumpers, so their tank needs a tight-fitting lid. SeriouslyFish
Electric Blue Acara
- The electric blue acara isn't a wild fish but a selectively bred captive colour form of the blue acara, Andinoacara pulcher. Maidenhead Aquatics
- Its parent species is named for the Andes plus “acara”, the Tupi-Guarani word for cichlids; pulcher is Latin for “beautiful”. SeriouslyFish
- Blue acaras are devoted biparental parents, the male guarding the spawning site while the female fans the eggs, sometimes swapping roles. SeriouslyFish
Firemouth Cichlid
- The firemouth flashes the bright red-to-orange underside of its head — most vivid in adults — giving the species both its name and its dramatic bluff. SeriouslyFish
- Its genus Thorichthys comes from the Greek for “to leap” plus “fish”, literally “leaping fish”. SeriouslyFish
- The species honours American ichthyologist Seth Eugene Meek, who compiled the first book on Mexican freshwater fishes. SeriouslyFish
Giant Danio
- The giant danio schools at the surface of small, high-gradient upland streams, feeding largely on insects that fall onto the water. FishBase
- True to its name, it's one of the largest danios, reaching about 15 cm (6 in) total length. FishBase
- It's a prolific breeder that can lay over 1,000 eggs, released in small batches of just 5–20 at a time. FishBase
Threadfin Rainbowfish
- Male threadfin rainbowfish grow extraordinary thread-like extended dorsal, anal and pelvic fin rays used to woo females and duel rivals. SeriouslyFish
- Displaying males raise the rounded first dorsal fin and “flick” their filamentous fins to entice a mate, often under floating plants. SeriouslyFish
- Iriatherina has stayed a one-species genus since 1974, and its rainbowfish family is most closely related to the freshwater fishes of Madagascar via ancient Gondwana. SeriouslyFish
Every fact here is drawn from a named authority — SeriouslyFish, FishBase, Animal Diversity Web (University of Michigan), Encyclopaedia Britannica, peer-reviewed research and Wikipedia for uncontroversial natural history — and checked against that source before it went up. We deliberately leave out the fun-sounding trivia that turns out to be a myth. How we fact-check →