Acting on hints of this kind, Mr. Lloyd has constructed aquaria with two reservoirs—one in a dark, cool place, quite large—the other in a light and warm place, favorable to the growth of plants and animals. By means of pipes these two reservoirs are connected so that a circulation can be set up between the light and dark portions. A pump may be used to force the water from the dark reservoir into the other, using vulcanite or rubber of some kind for sea water, instead of such oxidizable metals as brass, tin, lead, etc. The most convenient temperature is about 60° Fahrenheit.
Thus, by exchanging the waters of these two reservoirs, as occasion requires, we shall be able to regulate an aquarium so as to keep many kinds of plants and animals in a healthy, growing condition.
The best aquaria are those where the water is never changed, but ever circulated in the manner I have indicated. Water that has once been made clear and good, and maintained plants and animals, is better than any water newly brought from the sea. It must be remembered that evaporation takes place from the surface of an aquarium more or less according to the heat and dryness of the air. At a temperature of 60° in an ordinary dry air, such as occurs some miles inland, the evaporation from a surface of water six inches square would be about three drops in twenty-four hours. Some very warm, dry days it would be two or three times that much. This waste must be made up by adding occasionally some distilled water.
An aquarium must be kept free of decaying matter. If once formed the sooner it is got rid of the better, for it will poison all creatures that come within its influence. The larger the dark reservoir the better. It can not be too large, but should be not less than four or five times larger than the reservoir in which the plants and animals are kept. Any dead matter then will quickly be burned at a low temperature—for oxygenation by means of the dark reservoir means no more nor less than the burning up of the effete and decaying particles thrown off by plants and animals.
It might be profitable for me to tell now how I didn’t succeed with the first aquarium I undertook.
It was a fine, large structure, capable of holding some twenty gallons. The sea water was procured, and at low tide a friend went with me to help carry an assortment of plants and animals. We had read a good deal about the compensatory properties of these two kingdoms; how the plants exhale oxygen and inhale carbon, and how the animals inhale oxygen and exhale carbon, and thus preserve the equilibrium and the purity of the water. Well, we had good luck in searching tide-pools, and the turning over of rocks; and we returned loaded with snails, crabs, sea-anemones, sea-urchins, clams, abelones, date fish, real fish, sea worms (with beautiful red branchia), and sea weeds, an extensive variety of red, green and brown, only one or two of which would grow, as I have since learned, even in the most successful aquarium yet known. There are many other things that I have forgotten. We had rock-work and sand, and pebbles of beautiful colors, and a great many iridea, a rainbow-colored sea weed. We intended to imitate one of the beautiful tide-pools we had seen, and astonish our friends with a little bit of the sea, snatched up and transported to our quiet room, away from the fog and wind and chill of the ocean shore. We would willingly have brought the tide and some waves, if they could have been dwarfed to the dimensions of our tank. With these and a few other things we might have succeeded, and kept our aquarium as long as Robert Warrington kept his in London, with unchanged water, during a period of eighteen years.
But in eighteen hours our animals were all dead or dying; and although the plants were in proportion—that is, we had an equilibrium—they were almost equally in as bad a condition as the animals. First the water began to turn cloudy. We looked at our books for light, but they were equally obscure. Then we perceived a smell, somewhat like canned oysters, and this smell grew till it permeated the whole house. We suspected something wrong, so we emptied the aquarium, filtered the water, threw away the decaying matter, and put the things in again. But the “muddy vesture of decay” had covered the stones and entered the crevices, and in a few hours more we had to cast the contents away. The fact is, as I have learned since, we had a large number of bruised, broken and bleeding organisms from the handling in transfer, that the whole ocean’s waters could not save or heal, much less the little tank of twenty gallons. There were no waves to carry away the dead matter, no oxygen in the water to burn it, so it had to be breathed over and over again until the blood was poisoned and the animal died, because it could breathe such water no longer. And the plants began to fade and decay because their blood was also poisoned.
Now let us turn and consider for a moment Nature’s aquarium—the sea. It covers two-thirds of the earth’s surface, and it has been explored to the depth of eight miles at places, without finding bottom. The average depth, however, is about 2½ miles. All this immense mass of salt water is inhabited with a fauna and flora in a state of nature. That is, the hand of man has done nothing in the way of taming or cultivating them. They are absolutely wild, whilst a large part of the earth is subject to man’s dominion, and he was commanded to subdue it. The herbs and the trees of the field “shall be for meat,” and his “dominion over the fish of the sea, and over the fowl of the air,” pronounced at creation, is, as yet, but partially accomplished. The sea and the air remain as mysteries unsolved, and as powers unconquered. The cyclone and the tidal wave are evidences of the untamableness of these elements. “He bindeth up the waters in thick clouds, and the cloud is not rent under them,” was the language of some thirty-five centuries ago, and it is equally as true and expressive to-day.
Although the sea is inhabited at all depths, according to the best knowledge we have at present much the largest part lies beyond daylight. Light only penetrates a few fathoms—all below is darkness. This is the great, deep, cool reservoir from which the upper strata is constantly renewed by a circulation about which we, as yet, know but little. How is this circulation kept up? Who has charge of “the doors of the sea?” Who has “entered into the springs of the sea,” or “walked in search of the depth?” We have some knowledge in regard to these questions. The investigations of such men as Edward Forbes, Sir William Thompson, Dr. Wm. B. Carpenter, Lieut. M. F. Maury, Darwin, Kane, and a host of other scientific explorers equally as wise and industrious, have solved many mysteries in regard to the great ocean of salt water, and that lighter ocean of air that surrounds the earth.