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.
. Having now had a general view of the ponds, the reader's attention is directed to a detailed study of them, each one separately, the method of their construction, and the reason why they differ from one another; for, being made each with a specific purpose to serve, they of course must be built with that object in view.
The spawning-pond, or "propagating bed," is situated at that end of the rearing-pond where the water makes its entrance. It is a division consisting of a board frame eighteen (18) inches in depth and four (4) feet wide by eight (8) feet long, fashioned very much like the frame of a gardener's hot-bed. This frame, when ready, is to be sunk about two inches into the soil composing the bottom of the pond, and very accurately at that; for if this precaution is not taken, the fish are very apt to escape from the pond through any aperture that may be left. The upper edge of the frame should be not less than six inches above the usual level of the water, thus preventing the danger of overflow. In the side facing the supply drain, about two inches above the water level, and in the other forming the division of the rearing-pond, about one inch below this level, small openings for the entrance and exit of the water are cut and care-fully covered with galvanized iron-wire gauze, of about eight meshes to the inch.
This box, the bottom of which is formed by the floor of the pond, is to be covered with a well-fitting frame, mounted upon hinges and also covered with galvanized iron-wire netting of one mesh to the inch. This wire screen serves to prevent the approach of numerous enemies that would otherwise greatly interfere with the spawners, if not destroy them altogether. By following the above given directions for the construction of the frame the greatest economy possible can be had, for the lumber in the board as obtained from the dealers, measures twelve (12) and sixteen (16) feet in length, so that the measurements, eight by four feet, can always be had without unnecessary waste of lumber. Besides this, the wire netting is obtained in any length, and also four (4) feet in width, so that here too is a saving of material, and consequently of expense.
Inside of this frame, or box, as it may be called when placed into position, another frame upon which wire netting is stretched, is to be sunk. The size o the mesh is to be such as is best adapted to the size of the fish that are to be placed in the pond. It is very easy to see that this false bottom subserves a very useful purpose, and often saves time that at the moment is otherwise valuable. When, for one reason or another, it is desirable to remove the fish, the only requirement is simply to raise the frame to get it into shallow water, when the whole contents of the pond can be examined at ease.
A spawning-pond, such as the one described, can be, and with propriety too, constructed separately and wholly isolated. But if it is made a division of the rearing-pond, a good advantage is secured, namely, the stream of water that passes through it will carry into the rearing-pond such of the young fish as were hatched from undiscovered eggs. They will thus escape being devoured by the parent, and besides will get into the place intended for them, and where the chances for their growing up are vastly in their favor.
This is merely an apartment temporarily established in the storage-pond, which serves the purpose of protecting the young during their earliest infancy.
This pond differs from the preceding in several respects. To begin with, it is five times as large, the size eight (8) feet by twenty (20) being in many ways the most convenient, as experience has abundantly proven.
In constructing this, as well as the others, it is not absolutely necessary that the outlet should be directly opposite the inlet, though such an arrangement insures the most complete changing of the contents (the water) by the current passing from one end to the other. The location of the outlet and inlet must be determined by the judgment of the builder when seeking to get the best results he can, from the circumstances and surroundings of the locality in which he places his ponds. It is necessary, however, that the inlet • should be one or two inches above the water level, so that the fish will be prevented from getting into the supply drain, should there happen to be a defect in the guard. In constructing the pond, the remarks applying to ponds in general are to be respected. The dams must reach six inches above the water level, and the floor be as uniform as possible, with a regular incline of from six (6) inches depth at one end to twenty-four (24) inches at the other. The deepest part to be at the outlet, insuring a perfect and even drawing off, whenever that may be needed.
One or two plants, such as Nymphaea only, should be planted in the soil of the bottom, as their floating leaves afford shelter to the fish in very hot weather. Besides it offers greater convenience for the fish to reach deep water upon the approach of danger, as in such cases fish always dart to the bottom, and being there, they get out of the way much sooner. If placed near the outlet, it is also easier to gather the flowers when the plants are in blossom; this is probably a small point, but one that will be appreciated upon trial. Should the plants not be available, one or two pieces of board left floating on the water will answer the purpose. If it is impossible to isolate the rearing-ponds from each other, the consequences are not at all serious, but things should be so arranged that the very large fish are not mixed up with the small ones, as the latter would then be deprived of their share of the natural food the pond itself supplies.
This pond is for the sole purpose of keeping the saleable fish where they can easily be secured when desired, assorted according to variety, color and size, and kept in good condition till wanted.
It is to be so located that it will not interfere with the draining off of the other ponds.
Its construction does not differ in anywise from that of the rearing-pond, as indeed it can be used for rearing, if not wanted for nursery purposes (of which we will treat further on), until wanted for its destined purpose.
It is best, however, to divide it with boards into different parts of equal size, so as to secure a general fit of wire covers.
This is best located close by a spring, so that the constant flowing in of a stream of water of even temperature will prevent the surface of the pond from freezing over entirely, in which case the fish would die. The depth of the pond ought not to be less than three feet, and its sides closely lined with boards or masonry, thus affording protection from enemies and preventing caving in. The flow of water is to enter at one end, traverse the length of the pond, and leave at the opposite extremity. The dimensions of the winter quarters need not be very large, as during the winter season, fish in a natural state, pass that time in a semi-torpid condition, eat no food, and are not revived until they get the warmth of the sun in early spring.
A compartment of four (4) feet by eight (8), and of the above depth, will carry about fifty fish of eight to ten inches in length safely through the winter.
Where it can be done, the fish may be wintered over in a green house cistern, or in aquaria where they may be under close observation, and at the same time be of some ornamental value. If in the open air, the winter-pond is, of course, to be covered with wire netting to keep out the various birds and animals that would prey upon them; it is also well to protect the greater part of the top with boards, keeping out as much snow as possible.