There are a number of pretty and attractive fish suitable for a small aquarium, which can be obtained of any reliable dealer, while in a house where there are children the bigger boys and girls will find the collecting of suitable inmates from the neighbouring ponds, rivulets, and streams an absorbing holiday occupation, and the specimens thus secured will yield invaluable subjects for the ever-popular Nature study during term time or the intervals of lessons.
A small aquarium, if run on simple, scientific principles, should need-when once it has been successfully set going -only a few minutes' attention each day, for if the animal and plant life in the aquarium are correctly balanced, the water in the tank should remain bright and sparkling, and need rarely be changed, as the plants absorb the carbonic acid in the water, given out by the fish in the process of breathing, and in their turn generate the oxygen which the fish require. In order that this happy state of affairs may continue indefinitely in an endless see-saw of exchange, the aquarium must be prepared and filled with water, and the plants arranged in it and allowed to begin their growth for a week or ten days, in order to have thrown off a certain amount of oxygen into the water, before the fish are introduced, for it is essential that of the two the production of oxygen should exceed that of carbonic acid, and for this reason the aquarium should be understocked rather than overstocked with animal fife.
In order to discover the point at which the correct balance is maintained, introduce the fish-one or two at a time-and add more gradually until the capacity of the tank is arrived at. This may be judged in the following way. If the fish swim about happily well below the surface of the water, all is right; but directly they are
Collecting inhabitants for the home aquarium. Newts, tadpoles, and young fish can be secured by those who live near a pond or stream seen swimming in a more or less vertical position, with their mouths just below the surface, it is a sign of overcrowding. The oxygen supply in the water is insufficient, and unless a proportion of the inmates of the tank are removed, some of their number will certainly sicken and die in a short time.
A Suitable Tank
An oblong aquarium tank of convenient size, with a zinc-covered wooden bottom and glass sides, may be bought ready made for a guinea. In choosing it, see that its breadth is greater than its depth, so that a comparatively wide expanse of water comes in contact with the oxygen of the air. If a tank can be found with an opaque back, so much the better, otherwise it will be necessary to have a piece of wood or a strip of looking-glass fastened across the back of the tank, so that if stood in a window the light will not shine directly through it, for fish love cool and shady surroundings. The looking-glass back is an excellent plan, as it doubles the apparent size of the aquarium and number of its occupants to the onlooker.
The choice of aspect for an indoor aquarium is an important one. A north light is the best, and it must on no account be placed where the direct rays of the sun can ever reach it; while, on the other hand, a certain amount of light is necessary for the growth of the water plants and output of oxygen. The water in the aquarium must be kept at a low and level temperature; 50 ° Fahrenheit is the ideal, but it should never be allowed to go below 400 or above 60°. In very warm weather the tank should be moved into a cool, dark corner, or a lump of ice may be put into it to lower the temperature.
The first thing to be done is to provide sand and fine gravel for the bottom of the aquarium. River sand is the best for the purpose, but failing this bird sand answers very well. Before introducing either kind into the aquarium it will be necessary to scald it first of all in order to destroy any animal fife which might be lurking in it, and when this has been done it should be further washed in several different waters in order to thoroughly cleanse it. It must next be carefully sifted through a very fine sieve, and is then ready to use.
The aquarium must be washed inside, and the glass sides well polished, and the floor
Minnows and newts can be caught in a hand net may then be strewn with sand for a depth of two or three inches. A thin layer of fine gravel-probably the part of the bird sand which was left in the sieve after the sifting process will answer the purpose-must be now scattered over the sand, and the aquarium is ready to be further adorned with a rockery, in and out of which the fish can swim. If newts or water tortoises are to be included amongst the inmates, this rockery should be tall enough to come above the level of the water, to form an island upon which they can sit high and dry when the fancy takes them.
A little white-painted rockery, consisting of a couple of archways made of rockwork, may be bought with the aquarium for an extra shilling or two, or a satisfactory one may be made of pieces of pumice-stone fastened together with Portland cement, which is not affected by the action of water, or with wooden rivets -thick matches cut into suitable lengths with the ends pointed will answer admirably -the holes into which they are to fit being previously bored with an awl.
If the water plants are to be set in tiny pots amongst the rock-work, now is the time to arrange them; but if a few sprays of waterweed are all that are to be employed, they should be put in after the tank is filled.
In filling the aquarium tank great care must be taken not to disturb the sand, gravel, rockwork, and plants, if any.
Either a syphon made of a couple of lengths of indiarubber tubing, placed in a pail of water arranged above the level of the tank to be filled, must be employed, or a simpler plan is to fill the tank by means of a watering-pot with a very fine rose to it, the water being poured from it very slowly against the sides of the aquarium, and not directly on to the gravelled bottom.
When the aquarium has been filled with water some water-plants may be introduced.
The Canadian Waterweed is an excellent oxygen producer. It grows so quickly that it should be started in small sprays fastened to a pebble planted in the sand, and kept well pruned, or it will choke the aquarium. Italian Waterweed, or Val-lisneria Spiralis, which has tiny, delicate flowers, and looks very pretty growing in an aquarium, is also suitable as an oxygenator. It grows fairly well planted in the sand, but does better if planted in small pots in a good loam, covered with fine gravel, so that the loam does not wash out into the water. The Water Soldier is a third variety of water-plant which will float on top of the water, providing shade for the fish, or may be planted in the sand at the bottom of the tank. It is not so good an oxygen producer as the other two plants, and should therefore be used in conjunction with one or other of them, but its long, sword-shaped leaves and white flowers make it well worth a place in an aquarium. All water-plants should be kept carefully trimmed of dead, dying, or rusty leaves, which would soon pollute the water.
A simple and convenient way of planting any of these plants, suggested by the Rev. Gregory Bateman in his admirable book, "Fresh-water Aquaria," is to attach a small lead weight to the end of the stem and drop it gently into the water after the tank has been filled. A small hole can be poked in the sand with a piece of cane, and the gravel gently arranged round it, so that the lead is hidden.
There is an endless choice of occupants for the aquarium, but care must be taken to only put those together which will live in harmony, and for this reason the larger water-beetles, water-spiders, and water-boatmen are to be avoided entirely, for they prey upon small fish.
Half a dozen fresh-water snails should find a place in every aquarium, and will be found invaluable for keeping the glass sides of the tank clean and free from the alga, or green scum, which quickly forms unless these vegetable scavengers are at hand to remove it and to keep the inside of the glass bright and polished. A few fresh-water shrimps are also most useful as scavengers of fragments of animal matter which, if left undetected, would quickly pollute the water. They will find and devour remains of food, a dead worm or snail, for instance, with alacrity. Tiny fresh-water tortoises may be introduced if those are chosen whose carapaces measure less than two inches across, for larger ones are apt to devour the smaller fish !
Tiny goldfish cost threepence each, and small silvery dace and roach may be had for sixpence. A five-inch long eel will make an interesting addition to the inhabitants of the aquarium, and may be had for sixpence, while the snails may be bought for a few pence; water-tortoises cost a shilling each, and are, as has been said, useful.