50 Fun Facts About Aquarium Fish

Which English naturalist coined 'aquarium' and stocked the first public one at London Zoo in 1853?

He also wrote the first manual, The Aquarium: An Unveiling of the Wonders of the Deep Sea, in 1854, and launched a Victorian craze.

Which chemist showed in 1850 that plants in a water container could keep animals alive?

His 'aquarium principle' only works if the number of animals stays small, which is still the first lesson every fishkeeper learns.

Some of the earliest known fishkeepers were which ancient people, around 2500 BCE?

Fish were kept in ponds for food first; tame or brightly coloured ones gradually became pets instead of dinner.

The goldfish is native to which country, where it was first bred for colour more than 1,000 years ago?

It is a small member of the genus Carassius alongside the Prussian carp and crucian carp.

How long is a goldfish's memory span, according to research?

They can also tell apart shapes, colours and sounds, which puts the three-second myth to rest.

Why did the goldfish bowl become a thing in the first place?

Bowls are now considered bad for goldfish and are banned as permanent housing in some places.

The Bubble Eye goldfish is distinguished by fluid-filled sacs under its eyes and the lack of which fin?

The bubbles regrow if punctured, but they are notorious for getting sucked into filters and siphons.

The Siamese fighting fish, or betta, was first domesticated more than 1,000 years ago in which country?

They were bred for aggression and gambling bouts akin to cockfighting; King Rama III reportedly gave some to a Danish zoologist.

Which organ lets bettas and gouramis gulp air and survive poorly oxygenated water?

It is unique to the suborder Anabantoidei, which is why a betta can live in water that would suffocate most fish.

What do male bettas build at the surface of the water to attract a mate?

The male tends the eggs in it after spawning; some related bettas are mouthbrooders instead.

The guppy is named after Robert John Lechmere Guppy, who sent specimens to London from which island?

It had already been described in Venezuela in 1859; the honorific name Girardinus guppii came later and stuck as the common name.

Guppies, mollies, platies and swordtails are all what kind of fish?

They belong to the family Poeciliidae, and the male's anal fin is modified into a rod-like gonopodium for mating.

What is the gonopodium of a male guppy or platy?

It sits directly behind the ventral fin; female platies keep an ordinary fan-shaped anal fin.

The 'sword' of a swordtail is an elongated lobe of which fin, and on which sex?

The wild form is olive green with a red stripe; the female is actually the larger fish but has no sword.

Where does the platy get its common name?

It is also called the moonfish and can interbreed with the closely related swordtail.

The neon tetra, one of the most widely kept tropical fish, is native to which river basin?

Its iridescent stripe makes it visible to its own kind in dark blackwater streams, which is also why hobbyists love it.

The neon tetra's scientific name, Paracheirodon innesi, honours which aquarium author?

Myers described the fish in 1936; the cardinal tetra, described in 1956, was named for Axelrod instead.

How can you tell a cardinal tetra from a neon tetra?

On a neon the red stops about halfway to the nose, and its blue stripe is less vivid.

The freshwater angelfish of the genus Pterophyllum belongs to which fish family?

The name means 'sail-leaf' in Greek; they form monogamous pairs and will lay eggs on filter pipes if nothing better is offered.

Discus fish feed their fry for the first four weeks on what?

The so-called 'discus milk' is one reason the genus Symphysodon is famed for its parenting.

Marlin and Nemo in Finding Nemo are which species?

The film triggered a rise in demand for clownfish and blue tangs that was dubbed the 'Nemo effect'.

Clownfish are protandrous hermaphrodites, meaning what?

They live in harems with a strict pecking order; when the dominant female dies the top male takes her place.

Dory in Finding Nemo is which species, a favourite of marine aquarists?

Paracanthurus hepatus is the only member of its genus and goes by at least a dozen common names.

Which large South American cichlid, sold as the tiger or velvet cichlid, is also eaten as food?

It can reach 70 cm and 9 kg, and its tail 'eye spots' are thought to deter fin-nipping piranhas.

What does the name of the little armoured catfish genus Corydoras mean in Greek?

They are protected by body armour and sharp, typically venomous spines, and hobbyists track undescribed species by 'C-numbers'.

The common pleco is bought by hobbyists mainly for what job?

It can grow to 50 cm, and most fish sold under the name are actually other genera of armoured catfish.

Bristlenose or bushynose plecos belong to which genus?

The Greek name means 'fish hook', a nod to the curved cheek spines of the males.

The zebra danio of the pet trade is better known in laboratories as which model organism?

George Streisinger's zebrafish clones at the University of Oregon were among the first successful vertebrate clones.

Koi breeding for colour began in the early 19th century in which Japanese prefecture?

The word nishikigoi means 'brocaded carp'; the most popular group is the Gosanke of Kōhaku, Taishō Sanshoku and Shōwa Sanshoku.

A 1974 study of the scale rings of a scarlet koi called Hanako gave her age as what?

Most sources put a realistic koi lifespan at little more than 50 years, so the claim remains disputed.

With 1,760+ species, the cichlid family is second only to which family among fish?

Angelfish, oscars and discus are all cichlids, as are the tilapias on the fish counter.

Killifish eggs can survive partial drying out. Why?

Some 'annual' species live no more than nine months and are studied as models of ageing.

The word 'killifish' most likely comes from a Dutch word meaning what?

It has nothing to do with killing; a 'kill' is a creek, as in the Kill Van Kull.

Many gouramis have long, feeler-like rays at the front of which fin pair?

They use the feelers to touch and taste; the family is native to Asia from India to Korea.

A gold-stamped trio of which fish adorned the cover of the 1935 classic Exotic Aquarium Fishes?

The black triangular patch on its flank recalls a harlequin's costume, hence the name.

Why are coldwater and tropical fish generally not kept together?

Warm water speeds up a goldfish's metabolism and shortens its life; tropical tanks run at about 24–27 °C.

In the aquarium nitrogen cycle, bacteria convert toxic ammonia first into what?

A second group of bacteria then turns the nitrite into much less toxic nitrate, which water changes and plants remove.

In a reef aquarium, what is a refugium?

It often shares a divided tank with the sump, where the pumps and heaters live out of sight.

The tiger barb is endemic to which Indonesian island?

It is also called the Sumatra barb, and is notorious for nipping the fins of slower tank-mates.

The eel-like kuhli loach originates from which island?

It is nocturnal, has four pairs of barbels, and its eyes are covered by transparent skin.

The popular red cherry shrimp is a colour morph of a species whose wild form is what colour?

Neocaridina davidi has been bred into red, orange, yellow, green, blue and violet forms; it matures in 30 days.

The algae-eating Caridina multidentata shrimp is named after which Japanese aquascaper?

Also called the Yamato or algae shrimp, its larvae must drift to salt water to develop, so it rarely breeds in home tanks.

The White Cloud Mountain minnow's genus name Tanichthys honours whom?

Tan Kam Fe found it in the 1930s; it is now almost extinct in the wild but farmed by the million.

The German blue ram is a dwarf cichlid endemic to which river basin?

Females show a pink blush on the belly when ready to spawn; the whole fish is only 3–4 cm long.

Rainbowfishes of the family Melanotaeniidae come mainly from which part of the world?

The genus name Melanotaenia means 'black-banded' after the stripe along their flanks.

Where has the released pet goldfish become an invasive pest?

Released pets grow huge in lakes and rivers and stir up sediment, harming native species.

Betta splendens earned what nickname through centuries of breeding for colour and finnage?

It is one of more than 70 Betta species but the only one everyone calls simply 'betta'.

The guppy is also known by which nickname, a nod to how fast it breeds?

Native to northeast South America, it is now found on every continent except Antarctica.

Discus aquaculture is a major industry in which Asian country in particular?

The genus name Symphysodon refers to an unusual fusion of the teeth.

The oscar's yellow-ringed 'eye spots' near the tail are thought to deter which predator?

The oscar can also change colour rapidly, which helps it settle territorial disputes.