This section is from the book "The Goldfish And Its Systematic Culture With A View To Profit", by Hugo Mulertt. Also available from Amazon: The goldfish and its systematic culture.
An aquarium may be made of any water-tight vessel, the material of which will not alter the qualities of the water by impregnating it with anything that would stain it or give it an offensive odor, either of which would be detrimental to the health of the fish.
The shape of such a vessel is usually determined by the requirements of the duty it is expected to perform, and should not, therefore, be wider at the top than at the bottom, for then the fish would leap out; neither should it be too narrow at the upper part, for this would exclude the atmospheric air by a reduction of the water surface. The old-fashioned fish-globes are about the worst vessel that can be selected for the keeping of goldfish as pets; they will do well enough for a temporary display of the fish, but for permanent use they may be compared with the Black-hole of Calcutta. Besides they are extremely dangerous, in regard to their round shape, as there are several cases on record where fish-globes, hung near a window, set fire to the lace curtains or the carpet, the globe acting like a condensing lens.
When the vessel in which to keep the pets has been selected, it is thoroughly cleansed with water only, the bottom is then covered with well-washed river, or white sea-sand, to a depth sufficient to allow the planting of one or more varieties of aquatic plants. The number of these from which to make a choice selection is large, but in these pages only the leading and more desirable ones need be mentioned, the list being arranged according to their relative value as oxygenators. For use during the winter season, we select all or part of the following varieties:
Myriophyllum spicatum. Ludwigia Floridse. Cabomba viridis.
Sagittaria natans. Ceratophyllum rosaea.
Either one of these, grown as a single specimen, if of sufficient size, will do the work of aerating the water during the colder season.
If the tank is of a sufficiently large size, specimens of all of them may be introduced, and as all bear differently shaped and colored foliage, they will greatly enhance the attractive appearance of the aquarium. For the summer season we may make our choice from the following:
Ceratophyllum demersum. Anacharis canadensis. Sagittaria natans. Potomogeton pussilus.
Ceratophyllum rosaea. Vallesneria spiralis. Potomogeton crispus. Cabomba rosaefolia.
In both seasons we can add to the aquatics named, various kinds of marsh plants and those aquatics that float upon the surface, all of which add to the ornamental beauty of the collection. It may be mentioned that the plants put in a vessel containing fish are not placed there for the fish to eat, as many suppose. Some fish, however, have the habit of biting and tearing the plants from a spirit of mischief, very much like the restless horse that gnaws its crib.
This destruction of the plants can be obviated by placing in the aquarium such varieties as the fish objects to, for it is a fact that they manifest a liking for one kind and a repugnance to another.
The roots of the plants are imbedded in the sand, and bits of rock or pebbles placed around them to retain the plant in place, so that it will not be shifted about in the water. The vessel is then filled with "pure drinking water" to within a couple of inches of the top (See illustration); the water, if not fit to drink, can not be fit to be put in the aquarium, so that it is very essential that it be of prime quality.
When the water is in, one or two frog-tadpoles and a couple or more of pond snails are put in for the purpose of consuming any decaying vegetable matter that may appear, and to keep down as much as possible the growth of confervas; the number of tadpoles and snails must be determined by the size of the vessel and the rapidity of growth of the algae, etc.
When all these preparations have been made, the aquarium is ready to receive the fish.
Before they are put into it, however, the temperature of the water in the vessel in which the fish are brought must be equal with that in the aquarium. This is easily accomplished, and does not subject the fish to any risks that would either make them sick or be fatal to their lives.
When the temperature has been equalized, the fish are gently introduced to their future home, taking care that they are not plunged in so roughly that they become frightened. This performance may, under some circumstances, consume an hour's time, when, for instance, the fish have been carried a distance during severely cold weather, as then the changing of them from the transporting vessel into the aquarium must be made with great care.
The shape of the aquarium and the location in which it is placed determine the number of fish that can comfortably live in it. Should the location be bad as regards light, the amount of oxygen generated in the tank will be less, while if the situation is highly favorable in every respect, the evolution of the life-giving gas will reach its maximum degree.
The quantity of water required for a given number of fish is regulated by their size and the nature of the treatment they have received before they came into our possession. If, for instance, they were raised or had been kept in running water, or were newly caught in a large pond, they will naturally require a much larger quantity of water than if they had already been accustomed to a life of captivity.
As a rule, and it is a reliable one, each fish of three or four inches in length should be supplied with a gallon of water in which to live. Of course this norm may be disregarded for a limited period with impunity, but for the continuous welfare of the fish it must have its proper share of water.
The location of the aquarium should be such that the plants in it will be stimulated to their full capacity of growth, as this is the prime factor upon which depends the maintenance of the aquarium in a proper condition.
The subject of food is one that is but little understood by the majority of people, and is also a matter of no little importance. Most persons, in their anxiety to supply their pets, greatly overdo the thing; the waste material accumulating in the water, remains until it putrefies, thus polluting the water and rendering it detrimental to the health of the fish.
The feeding time should be but once a day, and that at a regular hour, the food to consist of flies or prepared fish-food, such as is obtained from the dealers. The quantity administered ought not to exceed what they will immediately consume. Once a week they may be given finely chopped fishing-worms, or raw beef scraped from the piece, but only in such quantities as to allow each fish a small mouthful. If any remnants of the last meal are found in the water, they should be removed at once, and the feeding entirely suspended for one or two days following. In cold weather the goldfish has but little or no appetite, while on the other hand, they eat voraciously in the summer. The best temperature for the water is somewhere between 6o° F. and 900 F., though the fish can stand it as low as 32° F. and as high as 110° F. without injury, if the change is not suddenly made, and a corresponding supply of oxygen present. Cold water retains the most oxygen, and also has the power of absorbing more of it from the atmosphere than warm water does. The warm water, however, is most favorable to the growth of plants, so that the quantity they furnish fully makes up the difference. It is poor philosophy to put ice into the aquarium to reduce its temperature, and it is equally foolish to wrap an aquarium in a bag and allow ice-water to drip upon it, as this is hardly the thing to do if the person cares anything for the parlor carpet.
When the fish come to the surface of the water to breathe, it is a sure indication that the oxygen has become exhausted. A fresh supply is easily introduced by simply stirring the water with the hand or dipping it up with a cup and pouring it back again, it is much better to do this than to put in a lump of ice.
The frequency with which an aquarium is to be cleansed depends altogether upon circumstances and the individual taste of the owner. An aquarium kept in the parlor of a suburban residence, and in a locality surrounded by flourishing shrubbery, needs re-arranging twice a year only, viz: in the spring and fall. On the other hand, an aquarium located in a smoky city and kept in a close, badly ventilated apartment, must be emptied frequently and a new supply of fresh water put into it.
Some people object very strenuously to the formation of algae upon the glass sides, and on that account clean the vessel very diligently, removing every particle they can find. Others again change the water because it does not form, their taste preferring the fish in all the natural surroundings of a rural locality.
The former carefully wipes each pebble till it shines, and would polish the fish too if it were possible, while the latter will walk for miles to some creek in order to procure some moss-covered rocks; so divergent are tastes in this matter.
. One must be able to exercise his own judgment as to the best time and when, for. the changing of the water in the aquarium, as it may sometimes be better to leave it undisturbed for some length of time, and at others to change it several times.
The best means to clean the glass sides from the adhering algae, when an aquarium is emptied, is by the use of a rough sponge or rag dipped in whiting; this will remove every speck without scratching the glass.
The best side of a room for the aquarium is that having a window, near which it is to be placed, as the light can be increased or reduced by opening and closing the shutters.
In the winter this position is the best, for the constant ventilation that goes on in the immediate vicinity of the window protects the water from the injurious effects of coal and tobacco smoke, and the poisonous fumes from the gas-burner; in the summer, in close hot weather, before a thunder storm, it can be easily and effectually aerated.
There remains yet one point: "Should the sun shine upon the aquarium?" This too is a matter of taste, though we would recommend a middle course, that is, let the fish have the sun part of the time. In winter allow them to enjoy the full light of the sun, but towards spring and during the summer shelter the tank from the direct rays.
If the goldfish are kept in water that contains no aquatic plants, it will have to be changed frequently as the oxygen in it can not, in most cases, be replaced from the atmosphere as rapidly as it is consumed by the fish.