The indoor aquarium is a very attractive feature in many homes, and is capable of being varied almost endlessly. It will furnish many hours of study and occupation. Its simplest form is the familiar globe for gold and silver fish, which can be set on a stand and forms a very attractive ornament. It should be kept about three-fourths full of water, which needs to be changed at least once a week. It is well to put a little washed gravel at the bottom, and some clean duckweed or other water-plant should be put in the water. These aid to keep up the sup- ply of oxygen, and the fish will nibble them occasionally. Small particles of bread or biscuit serve for food.
A larger aquarium is of much more interest. This is usually an oblong tank, with glass sides and ends, made water-tight. A glass plate can be laid over the top, with a narrow open space, so as to admit air and keep out dust. The tank should be bedded with clean, sandy gravel, which needs to be well washed, on which is placed some kind of rock-work, with a few chinks or crannies for retirement. These materials should be well boiled to destroy any undesirable growths. The plants needed may . be selected somewhat widely from aquatic growths. Some will root in the gravel; others, like duckweed, will float at large.
A few fresh-water snails are all the mol-lusks needed. For fish, almost any of the smaller kinds will do. The perch can be tamed to take food from the hand. The sticklebacks are interesting from their nest-building habits, but they are such fighters that it is necessary to keep them by themselves. The smaller fishes may be fed with insects, tiny bits of meat, and bread crumbs ; the larger occasionally with minnows. Worms are useful, and sometimes the only food available. Of other aquarium animals, the newts are pretty and interesting, swimming about with their olive bodies, or sometimes basking on the rock.
Keep only a few kinds of fish and other animals together. If scum collects, clean it off, or add another snail, which will do the work of an extra scavenger. If the inmates look sluggish and poor, replace some, of the water and aerate it well. See to it that a good supply of insects and small worms is put in as food; water-fleas, small larvae, etc., may be given freely. Take out at once any large dead or decaying thing. If all goes well, you need add only some rain-water now and then, to supply the loss by evaporation.