More Than 600 Varieties of Aquarium Pygmies Afford a Fascinating Field for Zoological Study in the Home

By Ida Mellen

This article was originally published in the National Geographic Magazine of March 1931 and is presented for historical interest!

It would be interesting to know in what country little fishes were first placed in glass receptacles for purposes of esthetic enjoyment. Rumor names Egypt; but, although the fresh waters of Egypt are replete with curious and beautiful dwarf fishes and the Egyptians developed the art of glass blowing during the Ptolemaic and Roman periods, after 300 B.C., there is no evidence that vessels of glass were used for aquaria.

The question can not be resolved with certainty, but it is well known that the lure of breeding fish in captivity took possession of the Chinese several hundred years ago, spreading to Japan, and thence over the Western World, with the goldfish as the original object of interest. During the past 75 years experimentation with the balanced aquarium has passed through various salt and fresh-water phases until, with tropical toy fishes, it has reached the peak of enthusiasm and success in Europe and America. ( See, also, “Goldfish and Their Cultivation in America,” by Hugh M. Smith, in the National Geographic Magazine for October, 1924)

Not that the goldfish has suffered a loss of popularity. Seventeen million are still reared annually in the Untied States, largely for martyrdom in the quart globe, and there is little diminution in the demand for bizarre and costly varieties. Among cold-water species it has no rivals.

Nevertheless, tropical fishes have superseded goldfishes in many of the smaller hatcheries, and some of the larger goldfish farms have built conservatories for rearing them.


Many shops in the larger cities are devoted exclusively to their sale, and a pet show without a display of these colorful midgets would be noticeable incomplete. But it is true, also, that, while most American and European homes have been ornamented at some time by the presence of a few goldfishes, the majority have not as yet succumbed to the allurements of the toy tropical, though fish “fans” spring up daily like mushrooms, enticed by the flash of color, the beauty of fin and form, the remarkable breeding habits undisturbed by captivity, and the ease with which the aquaria are maintained.

Many kinds imported into the United States are sold and shipped almost the length and breadth of North America – from Florida to Canada and from Massachusetts to California – but hundreds equally beautiful and interesting are as yet unknown to the fancier. The accompanying color plates present more than thirty kinds maintained in American aquaria, three-fourths of which have been bred in captivity.


The happy hunting grounds for toy fishes, explored and unexplored, range in the Western Hemisphere from the Carolinas south through Florida, and from Mexico through Central America, Panama, and South America to the most southern point of Argentina. In the Eastern Hemisphere, Egypt and other parts of Africa, Australia and Asia – including the island groups of the Malay Archipelago, India, China, Siam, and other countries – have been drawn upon for the supply of dwarf fishes appearing in the home aquaria of the Occident.

Tropical toy fishes are of many genera and species and even of many varieties – some natural, others cultivated. Their adult body length measures from one inch to five inches, the most minute of all not yet having been exported alive. These are four Philippine fresh-water gobies from Manila, Lake Buhi, Laguna de Bay, and Sitankai, in the Sulu Province, two of which reach a maximum length of one-quarter inch and two one-half inch.


The impossibility of transporting alive these smallest of all known vertebrates has precluded Occidentals, both laymen and scientists, from the enjoyment of one of the world’s greatest biological curiosities, the only specimen’s received having been forwarded in preserving solution; and the principal use to which the Filipinos put these tine creatures at present is a culinary one, many thousands being mixed with batter and baked into little cakes seasoned with herbs and spices.

From this we conclude that in flavor, as well as in nature and habit, dwarf fishes are not unlike their brothers of larger growth; but from the aquarist’s point of view they are separated into three diverse groups; the peaceable and the quarrelsome, the carnivorous and the omnivorous (few, if any, being wholly herbivorous), the oviparous and the viviparous (those laying eggs and those bearing living young and called “live-bearers:).

Subdivisions follow, such as delicate and hardy, prolific and unprolific, alkaline- and acid water species, and so on – details which may seem ponderous, but which the merest amateur masters quickly. The ichthyologist, on the other hand, recognizes the pygmies as belonging to definite species, genera, families, and orders, similar to fishes of normal size, and gives them Latin names (sometimes much longer than the little fishes themselves), which will identify them in any country of the world, for science speaks a universal tongue. The scientific nomenclature is known also to the fish fancier and even to the lad with his first pair of guppies.

Nor is the anatomy of the pygmies unique. Swim bladders and other organs common to larger fishes are common to them, and their fins are the same – caudal or tail, fins for swimming or propelling, fins beneath called ventral and anal, and pectorals (behind the gills) fro helping maintain the equilibrium; also dorsal fins (on the back), which indicate moods and physical states – health and contentment when erect, illness and depression when lowered. The majority have no defense against enemies except in such teeth as they possess.

Some are so peaceable that a number of species live amicably in one tank; others so quarrelsome that two males cannot occupy the same aquarium, and a male may kill his mate.

Some subsist largely on algae, but most favor small water animals, such as entomostracans (the minutest of crustaceans), annelids, and insect larvae; and the fish fancier may from time to time visit the wild ponds in search of their prey, rearing for them also, in boxes of humus, or leaf mold, the small whit earthworm, Enchytraeus of Europe and America, found from New Jersey to Maine, coastwise and along the shore, under stones and seaweeds; and whenever possible he supplies them with Daphnia, the tiny crustacean on which fancy goldfishes are reared.


But it is obvious that, if the finny tribe did not readily accept substitutes for live food, their maintenance in captivity would be impossible. Raw beef, cereals, roe, and shellfish, also dried shrimp and other desiccated foods, appear on their bill of fare, and many experiments have been made with concentrated foods, such as cod-liver meal and other glandular products, to ascertain their response to vitamin nutritives – experiments which have confirmed their amenability to a foreign diet and especially to substitutes for the lime, minerals, enzymes, and other catalytic agents present in live food, which aid digestion, purify the blood, and keep the skin lustrous.

The majority lay eggs and leave them to their fate, but some carry their eggs in their mouth, taking no food while incubation is in progress, and subsequently caring for their young, which swim back into the mouth at the approach of danger.

Some build nests and vigilantly guard the eggs and fry; others bring forth their young alive.


Nearly always when the fry receive any care it is given by the father, but in mouth breeding species it is usually the mother who gathers up the spawn, and among Cichlids, which include the Brazilian half-moon and Mesonauta, described in the accompanying biographies, both sexes guard the eggs and fry.

In yet another species, the Chanchito, the eggs are hatched in a nest scooped in the sand by the male fish. When able to swim the young rise and school, the mother leading the procession, the father bringing up the rear. The fishlets, allowed to swim only during the day, are stowed back in the nest at night.

In other species in which the male gives exclusive care to his progeny, his labors cease when they are able to fend for themselves. He suddenly apprises them of their independence by darting at them and eating a few, compelling the remainder to rush for cover. After that they know better than to trust any fish bigger than themselves. In aquaria, where they cannot escape, he usually eats them all, unless the mother precedes him to the feast, and the aquarist guards against this by removing either young or parents at the proper time.

Although these habits correspond in general with those of larger fishes, the latter do not breed in captivity, while a pair two inches long, in a two-gallon aquarium stocked with vegetation similar to that of their native habitat, and supplied with water of the correct quality and temperature suffer no nostalgia, and those equipped for breathing air accommodate themselves to smaller aquaria.

The only martyrdom to which the tropicals are subjected is accidental. Some expire from cold. Occasionally an aquarium is left uncovered and the fishes, many species of which leap like salmon, clear the rim with one jump and dry up on the floor; or an aquarist concerned for their comfort may transfer their tank to a radiator and forget until they are completely cooked.


Aquaria for tropical fishes are stocked with aquatic plants similar to those used in goldfish receptacles and may be of many kinds. The large-leaved Cryptocoryne, submerged spatterdock (Color Plates VI and VIII), and broad and narrow -leaved tape grasses (Sagittaria and Vallisneria, Color Plates I, IV, and V) provide the best oxygenation and for smaller aquaria the hair grass (Color Plate II) is much in favor because of its delicate green clumps, low growth, averaging four or five inches, and habit of producing new plants from rhizomes, like tape grasses.

More commonly sold in pet shops are anacharis, fanwort, and water milfoil, all with slight roots that require weighting with stones Anacharis (Elodea), a submerged herb of the frogbit family, (Color Plates I, II, III) is called “north American Waterweed” in Europe, where it was unaccountably introduced and has spread with great rapidity.

Fanwort (Color Plate VII) affords a depositary for adhesive spawn, and the firm ovate leaves and floating bulbs of the water-hyacinth (Eichhornia), as illustrated in the same plate, provide superior anchorage, for bubble nests, its feather roots furnishing excellent hiding and foraging jungles for fry and spawning grounds for fishes that cast their eggs among vegetation. Indoors, however the plant deteriorates, never choking an aquarium with the extensive growth with which it impedes navigation in Florida rivers.

Snails, familiar scavengers of the goldfish aquarium, figure also in the home of the toy tropical and have interesting habits. Pond snails with pointed spirals (Color Plates II and VI) and divers kinds of ramshorns, including the showy European red ramshorn (Color Plate IV), lay eggs in gelatinous masses which are devoured by the fishes. Snails in return eat the fishes eggs; and it is customary to remove them during the spawning season.

The Japanese viviparous snail (Plate VIII) brings forth living young with opercula, behind which they can retreat, and shells too tough for little fishes to manipulate.

For reasons biological, psychological, and social, the lure of the fish in the aquarium for many individuals is far greater that the lure of the fish on the line. This applies particularly to the pygmy fish, a hundred or more of the smaller species of which will live comfortably in quarters not commodious enough for a dozen goldfishes. When various kinds are placed in a sufficiently capacious receptacle, each species schools, thus massing and accentuating the colors.


Many facts of biological importance are to be discovered from a study of the toy fish. Abnormalities of shape and color – in other words “biological sports” – have not yet been taken advantage of, as in the rearing of goldfishes, to propagate new strains, though variation under domestication has given rise to many new varieties.

Thus far, experiments of breeders have been confined largely to hybridization, more with the expectation of producing an oddity, salable or otherwise, than of proving or disproving any principle of Mendelian inheritance, cross-breeding having been done with allied species of fighting fishes and Danios and related genera of top minnows (swordtails, moons, and guppies).

These non-scientific but interesting experiments seem to show that whether the male or female of a species is selected has a significant bearing on the character of the progeny, their color and “finnage” (a word coined by breeders). The expected sterility in the offspring does not occur or is confined to the male, and hybrids, especially among the top minnows, tend to be several times larger than either parent.

The great possibilities for the study of embryology, the development of new and desirable variations by careful cultivation, the extent to which the distribution of color and fin development are dependent upon agencies of temperature, environment, age, food, and other factors, and other biological features of the toy fish, commend themselves to the attention of the scientist, and in many a biological laboratory a collection of pygmies forms an important part of the equipment.

Lepidology, the study of the scales, in which the age of a fish is recorded, has not yet been applied to the pygmies to discover their natural term of life.


As among larger fishes, the young hatched from eggs are transparent, very delicate, and unable to feed, the umbilical sac (yolk sac) supplying nutriment for a few days and also retarding their movements. These require rich foods – love infusoria, diatoms, Daphnia; also the juices of meat and shellfish.

But pygmies born alive are as fully formed as adults, except in point of size and the development of the reproductive system. They are able to swim and feed immediately, and resemble nothing save two large eyes attached to an infinitesimal streak of animated protoplasm that can dart 25 times its own length in the minutest fraction of a second. These hardier youngsters, for whom nature makes no postnatal provision, thrive on prepared baby-fish foods, desiccated egg yolk, cracker dust, and oatmeal broth.

Males are generally smaller and more highly colored. Interbreeding has the same deteriorating effect as upon higher animals, and exchanges of breeding stock are made from time to time and new blood introduced through importations. Runts and giants occur in every batch, the former commonly disappearing down the gullets of the latter, though as careful selection is practiced by fanciers as in the cultivation of goldfishes and valuable plants. As yet, no purely albinistic stocks have appeared.

The psychology of the fish has been barely touched upon, and almost any careful observer may have the privilege of contributing new knowledge, for every fish is a law unto itself. Pygmies sometimes exhibit a discriminating sense of taste and an astonishing adaptability to change of environment, food, and temperature, and, when young, to the quality of the water they live in. Some are excitable; others phlegmatic; many active and playful. Some refuse to fight; others are incorrigible bullies. They learn most quickly where food is concerned and what time of day it may be expected. Some grow so tame they will swim into the hand; others never make human friends.

Exemplifying the dim dawn of vertebrate sensibilities, they display individual preferences and fierce jealousies; solicitude for their offspring or, in some cases, greater solicitude for the preservation of their own lives; some are curious and observing, showing an interest in form and color, being able to distinguish between the shadows of friends and enemies and between the two ends of the spectrum – that is, between red, orange, or yellow, as opposed to green, blue, or violet.

The young fish able to swim concerns itself very early with a recognition of its own species, and schooling has been observed among the fry of viviparous fishes less than a day old.


Exportations of toy fishes from Germany into the United States began about 25 years ago, numerous species having been first successfully bred in that country from parent stock captured in its tropical haunts. Though many thousands now are propagated elsewhere, a large percentage of those owned in the United States being “home grown,”considerable numbers, of a value variously estimated at from $50,000 to $100,000 per annum, still are shipped from Germany and South America.

The typical German traveling can is of tin, with a capacity of about four gallons, heavily insulated with felt wadding and paper and with an opening in the cover to admit air. Thousands of specimens have traveled safely across the ocean and into the interior of the United States in these cans, most of the shipping being done between May and October. For conveying by hand or shipping specimens shorter distances, one gallon thermos jugs are used.

Mechanics, chemistry, carpentry and aquatic biology all come into play in the keeping of the toy fish, and devices for its special care are numerous. In North America the temperature of the living room is adequate for the survival of some species, and they reproduce during the summer months; but the majority require water heated from 75 to 80 degrees Fahrenheit, and this is usually accomplished (in the suburban or country home) either by establishing the aquaria in a conservatory or specially heated room, or (in the city) by heating the tanks individually with alcohol or oil lamps, gas or Bunsen burners, incandescent lamps suspended in the water or electric heaters with thermostats for automatically regulating the temperature ( graphic on page 288 to be inserted).

Mechanical aerators for cloudy days, when plants fail to supply sufficient oxygen, are also in use, operated by water power or electric current and releasing oxygen in streams of minute bubbles finer that the spray from a watering can.

Among species that lay non-adhesive eggs and devour them, the female is placed in a breeding cage suspended in the aquarium. These cages are constructed of sloping wooden trays with small apertures through which the eggs may fall, or of glass, one popular type being made of glass rods narrowly spaced. With such a contrivance, the eggs come to rest at the bottom of the tank, the female can be removed to another aquarium after spawning, and in a few days the fry may be seen swimming about, secure from cannibalism.


More or less importance is attached to the quality of the water in which the toy fish is to live, Brazilian river fishes, like lake-dwelling species, requiring it less alkaline than those that live in or enter brackish water. With the help of chemical water testers similar to soil testers, acid sodium phosphate is used to produce the desired acidity, and plaster of Paris, calcium phosphate, or bicarbonate of so mixed with salt to create the desired alkalinity.

Europe boasts permanent and notable exhibits of toy fishes in a half a dozen of its public aquariums – those of London, Amsterdam, Antwerp, Berlin, Frankfort, and Leipzig. The United States lays claim to two. That of the Lincoln Park Aquarium, in Chicago, consists of 58 tanks, showing many brilliant species from the Orient and South America. That of the Steinhart Aquarium in San Francisco, consists of 31 tanks of similar species and, in addition, many brought from Samoa and Hawaii, which display the vivid colors and fantastic shapes that characterize the fishes of those waters.

When finished, the new John G. Shedd Aquarium, in Chicago, will display 65 balanced aquaria in a tropical-fish room maintained at a temperature of 80 degrees Fahrenheit, stressing beautiful setting and plant life rather than the rarity of the collection .

Besides these permanent exhibits, various societies of aquarists interested in both goldfish and tropical toy-fish culture hold annual exhibitions at which hundreds of aquaria are shown (the public usually admitted free), and prizes, including ribbons and silver cups, are awarded to both professionals and novices.

These societies exist for the purpose of stimulating both expert and amateur to greater interest by the exchange of ideas and specimens, some publishing instructive leaflets dealing with fishes, plants, successful experiments in rearing difficult species or breeding new varieties, and similar subjects. In the United States 25 such societies exist in Massachusetts, Connecticut, New York, New Jersey, Pennsylvania, Ohio, Maryland, Illinois, Missouri, Wisconsin, Washington, California, and the District of Columbia. The largest are in Newark, Jersey City, and Philadelphia.

The Newark Aquarium Society, having a membership of 500, at a recent exhibit visited by 50,000 people, displayed 1000 aquaria, with 160 classified varieties of tropical toy fishes ( graphic from page 305 in original to be included).

Many members of these societies, besides maintaining special rooms or conservatories for their collections, have private daphnia breeding reservoirs, hatcheries, outdoor pools, and other equipment, and it is not uncommon for one person to own 12 to 30 aquaria.

In the vicinity of such organizations are lodged numerous dealers in toy fishes, some with large conservatories and ponds for summer rearing.

The breeding of pygmy fishes for sale is an industry of steadily increasing importance in both hemispheres. Aquarium keeping is a pursuit (called by its followers a “hobby”) calculated to subvert any designs Satan may have upon idle hands, and to draw its devotees closer to the heart of the world of water life, so different from our own, yet urged and governed by such similar impulses – a pursuit in which familiarity breeds no contempt. Little fishes and the gods still are mentioned in the same breath.

Like dogs, some species are never absent, and others have their day of glory and almost disappear, with two or three always in the ascendancy. These are mentioned more particularly in the accompanying descriptions.


Mohammed’s dream of heaven was of a place through which flowed limpid rivers and lakes cool as camphor; and the clown in Urvashi says, “heaven is just a place where they never shut their eyes – like fishes!” The fish fanciers dream of Paradise is of a place overflowing with warm placid lakes that part like the Red Sea, allowing him to walk between natural aquaria and to view on a level with his eye, which he never shuts, millions of angelic counterparts of the pygmy fishes he so loved on earth.

In the brief delineations of the species presented in Mr. Hashime Murayama’s strikingly lifelike color portraits, the subjects are grouped according to their breeding habits: oviparous species of many families, which include a few that care for their eggs and young, and the labyrinth fishes, which blow nests of bubbles; and viviparous fishes of the family of top minnows.

Note: The original illustrations to this article will be posted at a later date!

Leave a Reply

Your email address will not be published. Required fields are marked *