CHAPTER XII

HINTS ON AQUARIUMS

It is better to have several aquariums than one. Often the mistake is made of gathering together all kinds of savage and voracious creatures that prey upon each other. Pretty as they are, there is no need to buy the glass aquariums, and indeed better in every way for the inhabitants is a large tub put out of doors in a place where there is not too much sun. Clean sand or gravel should be strewed upon the bottom and in this water-plants may be fixed. If you have any bivalves they will love to burrow in it, and some kinds of fish love to rest upon a bottom of this kind. Large stones should be built to reach half-way up the tub, with spaces between so that the fish may dart out of the light whenever they wish. If you keep fish that need running water it will be necessary to put the tub under a tap, and to pierce a hole near the top of the tub for the superfluous water to flow away. In this case it will be as well to cover the tub with a net, or the fish may be found to have leapt over the edge. Boys may make their own net from the instructions given in Chapter XIX., or may buy cheap gauze or other similar material.

If the tub is for newts and such things as do not live wholly in the water, then the stones should be built until they come above the water and so form a little island. For these creatures the water should not be so deep, and there should be an abundance of weeds.

Freshwater shrimps and crayfish should have a shallow tub or trough, a sandy bottom, and places in which they can hide. Here, too, there must be water running in and out always. By these means we imitate the natural surroundings of the shrimps and crayfish, for they delight in the running water of shallow streams that have a bottom of sand and stones. The outlet for the waste water should be protected with a grating and probably with gauze, or some of the inhabitants of the tub will escape.

There are many objections to glass vessels, though some of their faults may be corrected. They trouble the fish with too much light, but if a brown paper case of the same size and shape as the aquarium be made it can be slipped over the vessel and removed occasionally when you wish to observe the movements of the fish. Glass soon becomes foul, and needs frequent cleaning. In any case the aquarium should be kept out of the sun, and for this reason a northern window is best. Whatever form of aquarium is selected there must be soil and sand at the bottom, weeds, and shelter for the fish. The bell glass is the least favourable form of aquarium, but even that may be made tolerable if the hints we have given are adopted. In the square or oblong form only one side need be glass and the remaining three sides wood, metal or slate. The sand that forms the bottom of an aquarium should be quite clean. If you have found it in the bottom of a swift stream it will not need much washing, but if from any other place it should be washed thoroughly. Put a large bucket under a tap, and as the water runs into the bucket strew the sand gradually into the moving water with one hand, and stir the water as hard as you can with the other. Keep this going until the water that runs out of the bucket is quite clean. Even now, however, the sand may not be thoroughly cleansed. Put a drop of the water upon a piece of clean glass, and when the water has been evaporated there should be no sediment. When the sand, plants, pebbles and stones have been arranged in an aquarium it is best to introduce the water gently by means of a syphon, a method explained in Chapter XIX. The aquarium may be emptied in the same way.

There are a number of ways of supplying the fish with the amount of oxygen they need. One is to change the water frequently, another already mentioned is to have running water and a pipe for the surplus water; a third means is to have a fountain, an attractive element described in Chapter XIX.

These methods, however, are mechanical and artificial. The natural way of providing the oxygen is to secure the aid of water plants. These absorb carbonic acid gas, and, having made use of the carbon in their growth, set free the oxygen, which is waste as far as they are concerned. Thus in a well-balanced aquarium the fish provide the plants with carbonic acid gas, and receive back the oxygen which they need; the plants provide the fish with oxygen which they do not want, but which is the very life of the fish, and receive back the carbon without which they would die. Water-beetles, newts and some other creatures come to the surface for their air, and take no oxygen, or very little, from the water.

For many reasons the best aquarium is a pond in the garden, for here we may have greater variety of animal and vegetable life, and beautiful surroundings of plant life too. The pond should be about three feet deep, and the banks should slope, so that there will be a little spade work at first. The bottom may be of clay, but it is better for many reasons to have cement. The points mentioned with regard to the indoor aquarium apply here also, but many of the arrangements are more easily carried out in the pond than in the tank.

$Plants for the Aquarium.$--The duckweeds float and need no planting. They spread rapidly. There are four kinds: the Lesser Duckweed (_Lemna minor_); the Ivy-leaved Duckweed (_Lemna trisulca_). Then there is the American Pondweed (_Anacharis alsinastrum_), a weed that almost blocks slow moving rivers and canals. It will grow either attached to the bottom or floating. Not only does it supply the fish with air but with food also. The Hornwort (_Ceratophyllum demersum_) needs no soil, and gives off much oxygen, though probably not so much as _Vallisneria spiralis_, a great favourite in the aquarium. Easier to obtain is the Water Crowfoot (_Ranunculus aquatilis_), and we may mention also the Broad-leaved Pondweed (_Potamogeton natans_), Close-leaved Pondweed (_Potamogeton densus_), the Perfoliate Pondweed (_P. perfoliatus_), the Curled Pondweed (_P. crispus_), the Starwort (_Callitriche verna_), the Grassy Pondweed (_Potamogeton gramineus_), and the enterprising boy will find many others for himself in ponds, streams, and canals. Foreign plants are sold by dealers. For the garden pond the beautiful water lilies may be obtained. The weeds should be prevented from occupying too much space, and if the creatures in the aquarium do not keep them in check by eating them it will be necessary to remove some of the plants occasionally.

$Sanitation.$--If a fish dies remove it at once, or its dead body will pollute the water. To clean a glass aquarium let the water run away through a siphon until only a few inches remain, then clean the sides with a piece of rag tied upon a stick. Now siphon the remaining water away, at the same time supplying fresh water. Do not throw a lot of food to the fishes. What they do not eat decays and poisons the water. If there are molluscs in the aquarium this danger is lessened, for many of them act as scavengers, and they are assisted by freshwater shrimps, tadpoles, and beetles. The shrimps, however, may eat the living as well as the dead, and the tadpoles, instead of being allowed to eat, may themselves be eaten.

$The Food Supply.$--Fish eat the buds and tender shoots of pond weeds. They may have also a moderate supply of small worms, gentles, different kinds of larvæ, and what are called ants' eggs. Frogs and toads eat insects, little beetles, worms, grubs, caterpillars, and newts need an occasional worm.

$The Fish.$--Many of the fish that swarm in most ponds and streams are suitable for the aquarium. The carp is related to the goldfish, which is the golden carp. It is quiet and harmless, and will not interfere with other creatures in the aquarium. Minnows are pretty, and should have running water, and the roach is another suitable fish for life in captivity. The gudgeon, loach, and bullhead serve for bottom fish. Jack and sticklebacks are extremely interesting, but need a place for themselves, as they eat any other inhabitants of the same aquarium.

$Fishes as Pets.$--Perhaps, writes one of our contributors, the most interesting of freshwater fishes to watch is the stickleback, especially if a pair can be kept during the breeding season in a good-sized aquarium, so that they have the opportunity to collect materials and build their curious nest in the natural way.

The male fish develops during this season a most beautiful vermilion-coloured breast, and is exceedingly pugnacious, so that it is useless to attempt to keep two males in the same aquarium.

In fact, the stickleback is often so quarrelsome that it is not desirable to try to keep other fish with him, unless they are much larger than he is.

The easiest fish to keep alive are the carp (to which tribe the goldfish belongs) and the minnow.

These can be kept for years without much difficulty, and will not be likely to injure one another, or any other fish that may be placed in the same tank.

Small rudd are also very good pets, and are nearly as hardy and equally harmless.

Roach are easily obtained, and will not quarrel, but they are not quite so strong.

Perch, on the contrary, will live a long time if regularly fed, but it will not do to put any smaller fish, except sticklebacks, with them; yet they look so handsome that an aquarium containing two or three perch and a pair of sticklebacks is perhaps better worth looking at than one which can only boast of shoals of roach or other soft-mouthed fishes.

Dace and chub are pretty and harmless, but require more changes of water than is usually convenient, or they will soon die.

Tench are tenacious of life, but sluggish and fond of lying at the bottom. Small bream are fairly lively, and I have found them moderately hardy. They do not require water of special purity. Gudgeons live very well, and may be kept with minnows, being good friends together. The loach and the bullhead are fairly hardy, but have little other attraction. The grayling is very delicate, and it is not possible to keep her long, except under very favourable conditions. The ruffe or pope is hardy, like its relative the perch, and might, if obtainable (it is not a common fish), be placed in a perch tank, as a humble companion.

The bleak is almost as delicate as the grayling; and the jack is too ravenous for any fish to live in his company except another jack _of his own size_. This about ends the list, excepting that I've left till the last the noblest of fish--trout and salmon.

With regard to the latter I don't want to encourage a boy in the notion that he can keep a ten-pound salmon in a tank.

Nevertheless, I have for many successive seasons kept salmon for weeks or months in a small tank; but these were young ones, very young, about the size of tadpoles, in fact, and not unlike them in some respects.

They are almost indistinguishable from the young trout with which I keep them. Of course, they are but babies, and they have their feeding bottles attached, and do not want feeding till these are absorbed.

To return to trout. These fish, when about a year old, are very interesting, and if a constant change of water can be secured may be kept alive for years. Even without this advantage, I have kept them many months, and have found their little ways very curious.

The trait I objected to the most was the habit of cannibalism which the larger fish developed. I found one fish of about one and a half ounces with another about half that size half way down its throat.

This makes it desirable to keep only such trout as are about the same size together. They will gradually, though very slowly, get tame, and will come out from their shelter under a weed to eat a caddis as you drop it from your hand. This was only the case with some of the fish, others remaining as shy as ever in spite of petting.

It is best to choose fish that have been taken by net, but trout taken by a fly, or roach taken by a small hook in the lip, will live very well.

I have kept trout for months that I had caught with fly and carried home for miles. Some of these were from a quarter to half-a-pound in weight; but I found smaller fish would thrive better.

For food, caddis or other water insects are best; but gentles would perhaps do, if the former are not to be had. I found the freshwater shrimp capital food, as it keeps alive, of course, till the trout is inclined to eat. One of the chief causes of mortality in the aquarium is the fouling of water by the decomposition of surplus food. If you are obliged to use dead matter, such as chopped liver, or meat, be careful to remove any that may be left.

Flies may be put on the surface, and will be appreciated; but the trout will seldom take them while you are watching, though they will often eat the caddis as you put them in, and even chase the shrimps.

On the whole, I think perch are the best fish to make pets of, as they can be taught even to take worms from your hand, and require much less water running in and out than do the trout. I've known a perch to live for years in a tin bath in my stable; whereas the trout would not be happy without a long tank, and continual change of water.

If you have only a very small aquarium it may be better to be contented with a few minnows. These, with the water weeds and little fresh-water snails, which should be in every aquarium, will be quite enough to make it look pretty.