KEEPING A WINTER AQUARIUM
Instant aquariums, like instant pools, are easy to come by. Transparent plastic models, either produced as a single piece from a mould or composed of five separate sheets, are the most common aquariums. Plastic tanks do have the disadvantage, however, of scratching rather easily, and this is a serious disadvantage because algae will inevitably grow on the inside surfaces of the tank and these must be constantly scraped clean. To be sure, a plastic aquarium can, with care, be cleaned without scratching. But the risk is always there. By comparison a glass aquarium can be cleaned with impunity; and glass aquariums can be made up at home much more easily than you might imagine. And of course a homemade tank means a significant saving on cost. A glass merchant will supply five sheets of glass cut to the required sizes, and preferably with the top edges smoothed off (you can then put your hand into the tank without risk of grazing your wrist). Do explain to the glass cutter the purpose for which you intend using the glass. He should then appreciate that the sides and the base must fit together absolutely perfectly. And the tank should be designed so that the base sits within the four sides, not so that the sides sit upon the base. This is the way to make the most waterproof and permanent of joints. Nothing else is required but a tube of silicone rubber glue which a fish stockist will supply. This should be smeared thoroughly over all the edges that are to be joined together.
Match the four sides to the base — you may find four hands better than two for this operation — make sure the joints are perfectly aligned, then hold the lot together with sticky tape for about eight hours or until the glue has set. Silicone rubber, you will find, retains a high degree of flexibility, but the joints will be remarkably strong, as indeed they must. Ten litres of water weighs ten kilos, and yet this film of glue can well withstand the pressure that water exerts and more. The point to watch in applying the glue is that it is spread over the entire length of each surface to be joined. If this is done the tank will be quite free of leaks.
A cover for the tank will cut down on the amount of dust entering the water. It also serves a useful purpose in providing a ceiling to which lights can be attached. More important, if you intend keeping newts, a cover is essential to prevent them scrambling out of the tank. Plastic aquariums are usually supplied with plastic covers. If you have made your own tank, then plywood is probably the simplest material from which to make one. It need only extend beyond the sides of the tank by a few centimetres, but I would ensure that it was slightly raised over the tank to allow the free passage of air. A few wooden slats glued across the underside of the cover will achieve this. And a ‘lip’ of wood the whole way round the cover will hide the slats from view. It will also conceal whatever form of lighting you intend to use. Tubular fluorescent lights are the most suitable. They give off little heat which is an advantage and are economic in use. And since tubular lights are designed to be set in brackets there is no problem about attaching them to the cover. A single tube is normally quite sufficient. Remember to site it not down the middle of the cover, but towards the front. Positioned so, the illumination will be spread over the whole tank and not part of it; and fish swimming in the foreground will not be turned into silhouettes.
Whatever your confidence in your handiwork, common sense suggests you test your new aquarium either out of doors or in the kitchen sink. Once satisfied that it holds water right up to the top, empty it and place it on its permanent site. And permanent the site must be. The tank, if it is any size at all, cannot be moved again until it is emptied. Do bear in mind that the shelf of a bookcase may be sturdy enough for large, heavy books but not for a large volume of water. A sag-ging shelf can have disastrous consequences. And if the tank receives direct sunlight, it is imperative that you provide some form of shield or shelter for the fish. Small rocks are suitable and will add to the naturalness of your tank. Few aquarists, incidentally, would allow their tanks to get direct sun unless they were trying to change the colour of their fish. Rapid changes in temperature can be detrimental and sunlight encourages growth of algae. One other point is worth bearing in mind when siting an aquarium. Make sure you can get your arm over the top of the tank easily and without obstructions such as a higher shelf or an alcove ceiling that is too low. Cleaning a tank, introducing or removing fish, weeds, rocks or whatever, can be accomplished in minutes when access is free; otherwise you will quickly find it becomes a laborious chore.
Some aquarists favour growing oxygenating plants in a few centimetres of soil spread over the base of the tank, over which in turn a layer of gravel or sand is laid to prevent the fish muddying the water. Others are content to plant the oxygenators directly into sand or gravel. If you opt for using soil, obtain a light, poor-quality loam as free from decayingand organic matter as possible. Sand used either on its own or as a protective layer has a slight advantage over gravel. Particles of food and detritus cannot slip so easily between grains of sand as between nuggets of gravel. Fish and snails are then more likely to consume such items and there is less chance of pollution. Make sure the sand or gravel you use is quite free of soil or sediment. It should be sieved and washed clean.
If you have a seasoned, then I would fill up the aquarium with water taken from it. Failing that, rain water from an unpolluted rain barrel can be used. Be quite certain, however, that the barrel did not originally contain oil or chemicals. If neither of these sources of water is available then tap water must be used; letting it ‘settle’ for a few days before bringing in the fish may help to remove chlorine in the water. When filling the tank there is a simple way to avoid churning up the soil. Place a bowl on the bottom of the tank. Fill this with water and allow it to overflow slowly on to the surrounding sand and soil. The bowl can be removed once the tank is partially filled. A saving of work and trouble is to be made by planting your oxygenators in miniature flower — thumb pots as they are sometimes called — which can be buried a centimetre or less below the surface of the gravel or sand. An excellent practice is to have a number of these tiny pots in the outdoor pool, so that one has well-established, vigorous plants which can be brought in to serve the aquarium as required. Fish are partial to nibbling underwater foliage and will often divest a plant of all leaves, even when fish flakes or whatever are provided. Any of the oxygenating plants that you are using in the outdoor are suitable for the aquarium, with the exception of Callitriche stagnalis which prefers to be left out in the cold. Elodea is often used in aquariums. Fish seem to find its leaves succulent, but as there is always a plentiful supply of Elodea in any pond in which it is kept, there is no problem about replenishing it. The Tape Grass, Vallis-neria spiralis, and Curled Pondweed, Potamogeton crispus, are somewhat tougher and will last longer in the aquarium; and they are attractive in their own right. The oxygen exchange between the surface of the water and the sur-rounding air (when there is adequate space between the cover and the sides of the tank), and the activities of the oxygenating plants will satisfy the needs of a few fish. As a guide, for every centimetre of fish (excluding tail) one needs about 20 sq. cm. Of water surface. So a tank 36 x 25 cm. Could support 45 cm. Of fish. Far more satisfactory, however, is the practice of aerating the water by means of a miniature electric pump. Stocking rates can be doubled and the amount of electricity these pumps use is negligible. One end of a piece of plastic tubing is connected to the pump and the other end to an ‘aerator stone’ which gives off myriads of air bubbles when placed in the aquarium. As well as raising the oxygen content of the water, carbon dioxide and other noxious gases are forced out of the water. Even better than the aerator stone is the combina-tion of filter and aerator. This consists of a plastic with holes or slits along its top surface. Fibreglass padding is tucked into this container, sometimes with grains of charcoal underneath to act as a freshener. Air from the pump is circulated in the container and emerges in a series of bubbles. At the same time, the fibreglass filters out algae blooms, detritus and other waste matter, and when you scrape off the algae deposit from the sides of the tank, the filter will rapidly absorb what you have not collected in a fine net. An old razor blade makes the best kind of scraper for glass tanks but should never be used for plastic ones. The safest material with which to scrape algae off plastic is another piece of plastic, anything harder will almost certainly leave unsightly scratches.
Whenyour fish, turn off the pump so that food will not be absorbed by the filter container. If you have judged the amount of food your fish require, then there should be none left over. Fish are being adequately fed if they show enthusiasm for food without being frantic. They are most certainly being overfed if they show a take-it-or-leave-it attitude to newly introduced food, or leave large quantities of it untouched. And it is worth repeating that overfed fish become increasingly susceptible to ailments. Mature fish and fry must be kept apart. Either place them in separate tanks or use a dividing glass screen running lengthwise in one aquarium. A partition, incidentally, is sometimes used to prevent fish eating plants which are placed behind the screen as a background decoration. But cleaning a glass partition is troublesome. It tends to fall down or you cannot get your hands into the corners. Fish all too easily get into the wrong section. I would prefer to use two tanks where adult fish and fry are concerned.
If you want to keep newts to watch their courtship rituals and the antics of their little wriggling tadpoles, then they must be kept apart from fish. Newts will prey on small fish, and the Great Crested Newt is not above attacking its smaller cousins and its own young. And the tadpoles of frogs are liable to be preyed upon by both newts and fish, and not a few water insects as well. A garden pond, if one could only observe its depths, is like a watery Coliseum where the cycle of life is maintained by one creature preying off another.
If you are keeping only adult goldfish in the aquarium, and not fry, you can safely introduce a larger number of other creatures as well. Try sweeping your pond with a net and you should come up with a variety of life. Tubifex tubifex worms live with one end buried in mud and the other waving round above the level of the soil. They are easily recognized by being bright red. Fish are fond of them. You might be able to get hold of a Caddis larvae or two. They construct protective cases composed of small pieces of wood, grains of sand and other bits of material to be found on the bed of rivers and. If you push the larva out of its case with the head of a pin, you will have the opportunity of watching the process of case-building in the aquarium. The larva will not succeed in making quite as fine a case the second time round; nevertheless the process is a fascinating one to watch. Make sure the naked larva has access to some small twigs, leaves and sand. A sweep of your net through dense weed should produce a leech or two, which will snake through the aquarium at high speed. They are rather repulsive creatures though. I would prefer to find in my net some freshwater shrimps. I have always liked the way they busy themselves at the bottomof the aquarium, wandering around in their search for food. A Backswimmer or Water Boatman (Notoneda glauca) can be safely introduced if your goldfish are large, otherwise it is not worth the risk. A Water Boatman can pierce small prey with its powerful mouth, killing it at a single stab; and it is quite capable of giving your finger a nasty prick. The Water Boatman normally swims on its back with a characteristic jerky movement. When it dives, it carries down a store of air which adheres to the bristles on its body. You should notice the silvery appearance this gives the Water Boatman under water. Being lighter than water, it usually holds on to a piece of weed as an anchor when submerged. It would also be worth introducing some Daphnia magna or Water Fleas, which are quite tiny, about 5 mm. You can encourage their generation by steeping a little manure and decaying leaves in a bowl of water in the vicinity of your pond or wherever they are present. Daphnia should have some effect on the algae blooms in your aquarium since they off them, and the fish will in turn enjoy a meal of Daphnia.
And one should certainly include a number of snails. They too will feed off algae and detritus as well. Snails can live for long periods under water, but every now and again you will see them rise to the surface to take in air. Quite often you will see the curious sight of snails walking along the under-surface of the water, seemingly gripping the ‘skin’of water formed by surface tension. Touch a snail in thisand it will instantly sink to the bottom like a stone. This is not because the snail has let go of the skin of water, but because it has quickly expelled the air from its lungs when it sensed danger. Sometimes you may find the snail fearless, and it simply bobs up and down in the water as you push it with your finger. Having expelled air to sink, it can rise again by extending its body, so reducing the density of its body weight.
All these creatures and many more can be kept in an aquarium, and you might wonder if the aquarium could not become a miniature pond in which water-lilies, marginals and floating plants might not also be kept. In theory at least it is possible; in practice only partially so. The problem is that the amount of sunlight water-lilies and many marginals need, inevitably means a huge build-up of algae. Examine the walls of your outdoor pond and even though the water may be crystal clear, you will see algae blooms over vir-tually every centimetre of concrete or liner. An indoor conservatory pond can, of course, be built as easily as an outdoor one. It is the transparent sides of the aquarium that pose the problem.
If you want to try water-lilies indoors, they must have all the light possible. Miniature water-lilies are the obvious choice for small tanks (remember that snails are partial to their leaves). Among the floating plants, the duckweeds, Frogbit and Water Lettuce (given a high enough temperature) should do well in your aquarium. The Wateris obviously worth trying. It will flower in a warm room with plenty of sunshine. The Water Soldier is likely to be too big and cumbersome for most indoor tanks and prefers to be outdoors. The Lemnas are excellent for the small tank, as they make very pretty surface decorations. In particular, the fronds of the Duckweed appear altogether more dainty and attractive when viewed at close quarters. Indeed all plants and livestock will probably take on a different perspective in the indoor tank. Begin an aquarium and you may wonder if you ever really looked at all those plants and fish before.