50 free Aquarium Fish trivia questions with answers — nature quiz, new questions added Aug 2026.
This aquarium fish trivia quiz is for anyone who has ever stood in front of a tank and wondered. It covers the classics of the hobby — goldfish and their surprisingly long memories, bettas and their bubble nests, guppies, platies and swordtails, neon and cardinal tetras, angelfish, discus, oscars, corydoras, plecos, gouramis, barbs and loaches — plus the marine stars made famous by Finding Nemo, and the koi, shrimp and rasboras that round out a fishkeeper's world. It also digs into the science and history behind the glass: who coined the word aquarium, how the nitrogen cycle works, why bowls became a thing, what a refugium is, and which fish became a lab model organism. About a third of the questions are easy warm-ups; the rest will test people who know their Poeciliidae from their Loricariidae. If you like this one, our general fish trivia and jellyfish pages go further afield. Every answer has been checked against Wikipedia's species and fishkeeping articles and the sources they cite, and each explanation adds one more thing worth knowing.
30 of 50 questions with answers and explanations. Play the quiz
Q 01Which English naturalist coined 'aquarium' and stocked the first public one at London Zoo in 1853?
Philip Henry Gosse
He also wrote the first manual, The Aquarium: An Unveiling of the Wonders of the Deep Sea, in 1854, and launched a Victorian craze.
Q 02Which chemist showed in 1850 that plants in a water container could keep animals alive?
Robert Warington
His 'aquarium principle' only works if the number of animals stays small, which is still the first lesson every fishkeeper learns.
Q 03Some of the earliest known fishkeepers were which ancient people, around 2500 BCE?
Sumerians
Fish were kept in ponds for food first; tame or brightly coloured ones gradually became pets instead of dinner.
Q 04The goldfish is native to which country, where it was first bred for colour more than 1,000 years ago?
China
It is a small member of the genus Carassius alongside the Prussian carp and crucian carp.
Q 05How long is a goldfish's memory span, according to research?
At least three months
They can also tell apart shapes, colours and sounds, which puts the three-second myth to rest.
Q 06Why did the goldfish bowl become a thing in the first place?
Chinese pond fish were briefly shown in bowls for guests
Bowls are now considered bad for goldfish and are banned as permanent housing in some places.
Q 07The Bubble Eye goldfish is distinguished by fluid-filled sacs under its eyes and the lack of which fin?
Dorsal fin
The bubbles regrow if punctured, but they are notorious for getting sucked into filters and siphons.
Q 08The Siamese fighting fish, or betta, was first domesticated more than 1,000 years ago in which country?
Thailand
They were bred for aggression and gambling bouts akin to cockfighting; King Rama III reportedly gave some to a Danish zoologist.
Q 09Which organ lets bettas and gouramis gulp air and survive poorly oxygenated water?
The labyrinth
It is unique to the suborder Anabantoidei, which is why a betta can live in water that would suffocate most fish.
Q 10What do male bettas build at the surface of the water to attract a mate?
A bubble nest
The male tends the eggs in it after spawning; some related bettas are mouthbrooders instead.
Q 11The guppy is named after Robert John Lechmere Guppy, who sent specimens to London from which island?
Trinidad
It had already been described in Venezuela in 1859; the honorific name Girardinus guppii came later and stuck as the common name.
Q 12Guppies, mollies, platies and swordtails are all what kind of fish?
Livebearers
They belong to the family Poeciliidae, and the male's anal fin is modified into a rod-like gonopodium for mating.
Q 13What is the gonopodium of a male guppy or platy?
A modified anal fin used for mating
It sits directly behind the ventral fin; female platies keep an ordinary fan-shaped anal fin.
Q 21Marlin and Nemo in Finding Nemo are which species?
Ocellaris clownfish
The film triggered a rise in demand for clownfish and blue tangs that was dubbed the 'Nemo effect'.
Q 22Clownfish are protandrous hermaphrodites, meaning what?
A male can change into a female
They live in harems with a strict pecking order; when the dominant female dies the top male takes her place.
Q 23Dory in Finding Nemo is which species, a favourite of marine aquarists?
Regal blue tang
Paracanthurus hepatus is the only member of its genus and goes by at least a dozen common names.
Q 14The 'sword' of a swordtail is an elongated lobe of which fin, and on which sex?
The tail fin of the male
The wild form is olive green with a red stripe; the female is actually the larger fish but has no sword.
Q 15Where does the platy get its common name?
Its old genus, Platypoecilus
It is also called the moonfish and can interbreed with the closely related swordtail.
Q 16The neon tetra, one of the most widely kept tropical fish, is native to which river basin?
The Amazon
Its iridescent stripe makes it visible to its own kind in dark blackwater streams, which is also why hobbyists love it.
Q 17The neon tetra's scientific name, Paracheirodon innesi, honours which aquarium author?
William T. Innes
Myers described the fish in 1936; the cardinal tetra, described in 1956, was named for Axelrod instead.
Q 18How can you tell a cardinal tetra from a neon tetra?
Its red runs the whole body length
On a neon the red stops about halfway to the nose, and its blue stripe is less vivid.
Q 19The freshwater angelfish of the genus Pterophyllum belongs to which fish family?
Cichlids
The name means 'sail-leaf' in Greek; they form monogamous pairs and will lay eggs on filter pipes if nothing better is offered.
Q 20Discus fish feed their fry for the first four weeks on what?
Mucus secreted from their own skin
The so-called 'discus milk' is one reason the genus Symphysodon is famed for its parenting.
Q 24Which large South American cichlid, sold as the tiger or velvet cichlid, is also eaten as food?
Oscar
It can reach 70 cm and 9 kg, and its tail 'eye spots' are thought to deter fin-nipping piranhas.
Q 25What does the name of the little armoured catfish genus Corydoras mean in Greek?
Helmet skin
They are protected by body armour and sharp, typically venomous spines, and hobbyists track undescribed species by 'C-numbers'.
Q 26The common pleco is bought by hobbyists mainly for what job?
Cleaning algae as a bottom cleaner
It can grow to 50 cm, and most fish sold under the name are actually other genera of armoured catfish.
Q 27Bristlenose or bushynose plecos belong to which genus?
Ancistrus
The Greek name means 'fish hook', a nod to the curved cheek spines of the males.
Q 28The zebra danio of the pet trade is better known in laboratories as which model organism?
Zebrafish
George Streisinger's zebrafish clones at the University of Oregon were among the first successful vertebrate clones.
Q 29Koi breeding for colour began in the early 19th century in which Japanese prefecture?
Niigata
The word nishikigoi means 'brocaded carp'; the most popular group is the Gosanke of Kōhaku, Taishō Sanshoku and Shōwa Sanshoku.
Q 30A 1974 study of the scale rings of a scarlet koi called Hanako gave her age as what?
226 years
Most sources put a realistic koi lifespan at little more than 50 years, so the claim remains disputed.