A PRACTICABLE WAY TO STUDY MOLLUSKS ALIVE IN YOUR OWN HOME About fifty years ago a young lady up in Vermont took home from a pond a two-quart glass jar of water in which she had collected a few tadpoles, minnows and snails, and some of the growing pond-weed among whose leafy stems she found them. In her home she kept this happy family; the water did not stale and grow turbid; the animals and plants throve as if they were still in their native pond.
The secret of her success was this. The leaves of submerged plants give out oxygen which gill-breathing animals obtain from the water. They take up the carbonic acid gas given off into the water by the animals. Each kind of living thing needs the very element that the other discards. Plants and animals "purify the water" for each other. This balance of Nature is a nice one. Too many animals or too many plants upset it.
Fresh water aquaria are miniature ponds, tanks or jars stocked with animal and plant life brought in from ponds or streams. If properly "balanced," the water needs no changing but remains pure and sparkling as long as the equilibrium is maintained. This is the practicable aquarium for all who live inland.
Marine, or salt water aquaria are feasible for all who live near the seashore. The law of balance holds here, too. The difference is that sea water is used, and seaweeds and the animal life of the ocean furnish the proper materials for stocking it. Inland, there have been some successful marine aquaria. But it is expensive to ship sea water by rail, and making artificial sea water presents many difficulties. The stocking of these aquaria is precarious business. Successful marine aquaria inland are rare.
Public aquaria, like the great institution in Battery Park, New York, which is visited by thousands of people daily, maintain 9 The Balanced Aquarium and the Snailery full-grown specimens of various animals that live in the seas as well as in rivers and lakes. For such, the water in the tanks requires constant change, or the inhabitants would die. There is a pipe bringing in a fresh supply, and an exhaust pipe carrying off the excess in each tank. The greater the surface, the better
chance for fresh air, which plants and animals all need. Many animals come to the surface for air. The best aquarium imitates the pond in having the largest possible surface in proportion to its depth.
A tank fitted with running water is too elaborate and too expensive an outfit for home use. The care of it soon becomes a burden.
The Home-made Tank.—The image that arises in the average mind is of a tank made of an iron frame, plate glass and cement, with a large rock-work piece in the centre. Through the arch ways and colonnades, and in and out among waving plumes of water plants there passes a procession of gay gold fishes.
Let me counsel the beginner to curb his aspiration for a home-made tank. Materials cost little, and it looks reasonable to suppose that a good mechanic can put them together success fully by simply following directions. The experience of many an ardent aquarist has been that failures succeed failures, no matter how carefully he has tried to forestall them. "Water is so thin! It will work through anywhere." Changes in tem perature, warping of the wood, cracking of glass, disintegration of the cement in spots—these are contingencies that keep the builder of a home-made tank in constant suspense. The leak he anxiously expects for months is sure to come, like a thief in the night, to ruin his hopes. If you must have an aquarium of this type, buy it of a dealer who will guarantee it, or make good, if any faults in construction come to light. Thus risks are mini mised, and the owner can sleep o' nights.
Solid Glass Aquaria.—Rectangular tanks in one piece" are very satisfactory. Examine them before buying, to be sure that objects are seen without distortion through the sides. Choose one as nearly uniform in thickness as possible. The fault of these jars is that in moulding the angles are likely to be thinner than the sides, which makes them liable to crack when the temperature is variable.