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A Salt Water Aquarium by A. W. Roberts



Hundreds of young people are now spending their vacation on or near the sea-shore, and have a good opportunity to study the wonderful habits of animal and vegetable marine life. Therefore I have undertaken to throw out a few plain hints as to the management of a salt-water aquarium, in which these interesting forms of nature can be observed to greater advantage.

We will start off with one of the small tin frame tanks sold in New York so cheap, or a candy jar, or a small-sized wash-tub—any vessel that will hold water, and is not of iron, tin, or copper, either of which will poison the water.

After washing out the tank carefully, and filling it with clear sea-water, we will place in it twelve silver-shrimps (bait shrimps). At the end of two days they are dead, and you ask why did they die when they had so much water to live in. They died of suffocation, after they had breathed all the air contained in the water. We will take out the dead shrimps, and in the same water place a good handful of ulva (sea-lettuce, sea-salad), one of the most common of all marine plants, and place the aquarium in a strong and direct sunlight, by this means exciting the ulva to work, or, as it is termed, aerify the water. In less than an hour's time a froth will be seen forming on the surface of the water, and adhering to the sides of the aquarium. Now observe the ulva closely, and from its edges and surface very fine threads of silvery bubbles are pouring out and ascending to the surface. In an hour's time the water will be thoroughly charged with air. We will again place twelve more shrimps in the aquarium. This time they will live, and we will have established a true aquarium—an aquarium based on the self-sustaining principles of nature, wherein it will not be necessary to change the water.


Fish as well as human beings breathe air. Air is contained in all water. After the shrimps had breathed or used the air contained in the water several times over, it became unfit to sustain animal life any longer, and so they smothered: just the same as if a number of people were placed in a room, and all the doors and windows and ventilators were sealed up tight, so that no new air could enter. They, too, would suffocate in a short time and die. All plants living in water are constantly manufacturing new and pure air for their friends and companions the fishes, particularly when under the action of sunlight.

The great secret in establishing a self-supporting aquarium is to establish a natural balance of water, fish, plants, and light, so that none of these agents are wanting in quantity. For instance, a strong light is required to cause a healthy development of the plant life, but not direct sunlight, or the plants will be forced too rapidly, and death will soon follow. Again, direct sunlight will increase the temperature of the water to such an extent that many of the fish will die. If the animal life is in excess of the plant life and the water contained in the aquarium, the animals will perish for want of sufficient air. Again, if the aquarium is overstocked with plants, so that they are crowded so closely that the light fails to reach some of them, decomposition will take place, and everything will become a decaying mass. In fact, it is only by beginning on a very modest scale, with a very few and small fish at first, and by gradually increasing the number, that a beginner can expect to succeed. Over-stocking with animal life and overfeeding are the two greatest temptations that beset the path to success for the aquariumist; but patience, perseverance, and critical observation will eventually lead to success.


The greatest care must be taken, and all shells, rock-work, sand, and plants must be washed over several times, so that no injurious substances may be introduced.

Ulva, or sea-lettuce, is to be found in abundance in all our small bays and inlets at low tide. For the aquarium, those specimens which are thick in texture, and of a dark green color, only are fit for manufacturing air. Never be tempted to make use of the light green and thin specimens, as they are not sufficiently matured, and will soon decay if placed in the tank.

Scallops when young have a curious way of changing their location by means of opening their shells and then closing them with great force, which sends them off at an angle, and so they go dancing along the bottom till they reach a spot that suits them. This shell-fish forms a beautiful addition to an aquarium.


The silver-shrimp, with figured back (all other varieties must be avoided), I have always considered as constituting a Board of Health in an aquarium; for no sooner does the water become unhealthy than these transparent and grasshopper-like creatures will make desperate attempts to jump out of the tank. These shrimps, and the little hermit-crab, and the buccinum (a small black sea-snail) are Nature's house-cleaners. They are always on the look-out for decaying animal or vegetable matter, which, if not in too large quantities, they speedily devour.

I have seen these black snails gather on a dead fish from a distance of half a mile; in less than a day's time nothing was left of the fish but his bones and scales, and these were picked so clean that they had a polished look. These snails are provided with ribbon-like tongues, from which project a great number of minute and beautifully constructed teeth. By passing these tongues backward and forward rapidly they cut their food down much as a mowing-machine cuts grass. These snails are the scavengers of all dead fish and vegetable substances found in our bays and rivers, and to them we owe a great deal of the purity of our waters.


The little hermit-crab lives alone in an empty shell, which he carries about with him wherever he goes. His reason for living in a shell is because the hind part of his body is soft, and not protected with a hard shell, like the fore part of his body. The end of the soft body of the hermit-crab is provided with hooks, or claspers, with which he holds on to the inner chamber of his shell so tightly that it is almost impossible to get him out except by breaking the shell. Very often these crabs are to be found with a colony of living polyps growing on their shells. These polyps are very interesting from the fact of their being the parents of one of our most beautiful jelly-fishes.

When a hermit-crab grows too large, or so fat that his shell pinches him, he hunts up a new one. First he pushes his long claws far into it, just to see that no one is inside, and that it is nice and clean; then he rolls it over and over, often lifting it so as to judge of its weight. If it suits, he drags it close to the entrance of his old home, and in an instant he has whisked into his new house. Hermit-crabs are great house-hunters, often moving just for the fun of it. They are always skylarking with one another like monkeys, and, in truth, they are the monkeys of an aquarium. When the water in an aquarium becomes bad, they are sure to indicate it by leaving their shells, and trying to crawl out of the tank. In all respects they are the most valuable and interesting inhabitants of the aquarium.


Pipe-fish are apt to be delicate; still, if your aquarium is in perfect health, and the water is teeming with minute animal life, they will get along nicely. Their favorite food consists of the eggs of all small crustaceans, such as shrimps, sand-hoppers, and lady-crabs. Mrs. Pipe-fish does not take care of the children, but Mr. Pipe-fish places them in a long folding pocket that runs along the under side of his body (which I have tried to show in the engraving). When he lets them out of this pocket into the vast ocean world to shift for themselves, they are only a quarter of an inch long, no thicker than a bristle, and almost transparent.


Think of a crab decorating himself with bright-colored sea-weed, so that he is called the dandy-crab! Still, he is not so vain, after all, as he covers himself with sea-weed that he may escape the sharp eyes and sharp teeth of hungry fishes. I once had a dandy-crab whose back I had scrubbed clean, after which I placed him in an aquarium containing a plain sand bottom. In this tank I also placed a hungry black-fish, who soon took a nip at him, securing only one of his legs. This so frightened the dandy-crab that he began searching over the aquarium for material to cover himself with. In the tank I placed several sea-flowers (anemones), cut into small pieces. These he immediately seized, and soon had them fastened over his back, using both claws, he being both right and left handed, and sticking them on with a kind of glue that he took from his mouth. In a few days the pieces of sea-flowers began to develop into perfect flowers, causing the crab to look very gorgeous.

When a crab loses a claw, he does not mind it; in fact, he rather likes it, as it provides him with an extra meal. All he does is to sit right down and bite it off to the next perfect joint, eating the fragments of flesh with much relish. In a week's time a new claw begins to grow. When a spider-crab grows too large for his clothes, he rips them at the back, and out he slides, a helpless soft mass. He is now a "soft crab," and for thirty-six hours he has to hide away, as all fish are hunting for soft-crab dinners. At the end of thirty-six hours he is hard again, and has increased one-third in size.


Of all laughable fish a baby swell-fish is the funniest. Beautiful in color, odd in shape, with the power of blowing himself up into a round ball covered on the under side with spines, does he not look wise and important? And he has only two teeth, but can't he bite? Why he swells himself up so is not exactly known; but I imagine that when he finds himself inside of a fish, he makes it so uncomfortable for that fish's general health that the fish is glad to get rid of him.


Next to a young swell-fish comes a young sea-robin, a very interesting fish. He can make a musical grunting noise when he feels good, and will spread his beautiful wings, and sail through the water as proud as a peacock. When he is tired, he likes to bury himself up to his eyes in sand, for which he uses his two curious hooked fingers. He also uses these to dig out the sand-shrimps. Some years ago great numbers of very large sea-robins visited our coast, and were sold in the New York markets under the name of Dolly Vardens, on account of their possessing such bright and showy colors.


The shell-fish known as the oyster drill is one of the greatest of all enemies to young oysters, which he destroys by boring minute holes through their shells, and when the oyster opens, after death, eating him up. It is not known how he drills this very minute hole so quickly.


The clinker (serpula) is really a vast marine tenement-house for a social community of beautiful sea-worms, who build up houses of shelly tubes twisted and fastened together. Each worm has a stopper, or cork, to his shell, with which he can close up the entrance to his house.

When this sea-worm is feeding he throws out from the entrance of his tube a beautiful double plume. These worms are the favorite food of the sea-horse, who sucks them out with a sharp snapping noise.

The sea-horse is considered to be one of the greatest prizes that can be obtained for an aquarium. For dignity of carriage, grace of motion, and beauty of form, he excels all other fish. The papa sea-horse takes care of his children the same as the pipe-fish, to which he is closely related; only his pocket is in front of him, and is much larger, and different in shape. This pocket is lined inside with a fatty substance, on which the young sea-horses feed till they are strong enough to be crowded into the world. The sea-horse, when he thinks it time to turn out his children, presses his big pocket (for he has no hands nor claws) against a shell or piece of stone, and out swim the young horses. At first they are apt to form into bundles by locking their tails together, but as they become accustomed to their new surroundings, and are stronger, they separate. The male sea-horse displays much pride over his young, and remains with them several days. Sea-horses can look two ways at once, as each eye moves independently of the other.


The tube-flower is very common along our coast. It lives in a long, thin, light-colored tube, composed of a material resembling horn. It has the power of stinging slightly, but, for all that, is so beautiful that no aquarium should be without it. This animal casts off its flower, or head, every few days, after which a new one makes its appearance.

Sea-flowers (anemones) are always to be found in the same locations with tube-flowers. Just to think of taking an animal that moves and eats and breathes, and cutting him up, and that each piece will become a perfect animal again! Yet such is the case with sea-flowers. When they wish to produce young, they tear off pieces from their bodies (the base parts), which soon develop into young sea-flowers. In the illustration I have shown three kinds of sea-flowers, all of which are common on our coast. The inside part of a sea-flower is divided by many partitions, forming a circle of store-rooms; into these rooms he passes his food, where it remains till all the juices are extracted, after which he passes it out again the same way it entered. The colors and forms of all our sea-flowers are wonderfully beautiful. Their thousands of hands (the fringe-like part), which are constantly moving in all directions in search of food, remind one of an animated aster.

Small groups of acorn-barnacles, when attached to stones or wood, are very desirable objects for the aquarium. For a few hours after being placed in their new home they will remain closed, but as soon as they become accustomed to their surroundings, one after another will cautiously throw out his feathery casting-net in search of food. Then the reaching and grasping become so rapid and general that the eye can hardly follow their motions.

I feed my fish three times a week with soft or hard shell clams cut fine, taking great care that no food remains uneaten to taint the water. For bottoms for aquariums I use coarse bird-gravel, or pebbles thoroughly washed, with small masses of rock-work.