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AQUARIUM (plural aquaria)
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See also:AQUARIUM (plural aquaria) , the name given to a receptacle for a marine See also:flora and See also:fauna. Until comparatively recently,
AQUARIUM 237
aquaria were little more than domestic toys, or show-places of a popular See also:character, but they have now not only assumed a profound scientific importance for the convenient study of anatomical and physiological problems in marine See also:botany and See also:zoology, but have also attained an economic value, as offering the, best opportunities for that study of the habits and environment of marketable See also:food-See also:fish without which no steps for the improvement of See also:sea-See also:fisheries can be safely taken. The numerous " zoological stations " which have sprung up, chiefly in See also:Europe and the See also:United States, but also in the See also:British colonies and See also:Japan, often endeavour to unite these two aims, and have in many cases become centres of experimental See also:work in problems See also:relating to fisheries, as well as in less directly See also:practical subjects. Of these stations, the See also:oldest and the most important is that at See also:Naples, which, though designed for purely scientific See also:objects, also encourages popular study by means of a public aquarium. The following See also:account (1902) of this station by Dr W. Giesbrecht, a member of the See also:staff, will serve to show the methods and aims, and the complex and expensive equipment, of a See also:modern aquarium:
" The zoological station at Naples is an institution for the See also:advancement of biological science—that is, of See also:comparative See also:anatomy, zoology, botany, See also:physiology. It serves this end by providing the biologist with the various objects of his study and the necessary appliances; it is not a teaching institution. The station was founded by Dr Anton Dohrn, and opened in the See also:spring of 1874; it is the oldest and largest of all biological stations, of which there are now about See also:thirty in existence. Its two buildings See also:ate situated near the seashore in the western See also:town See also:park (See also:Villa Nazionale) of Naples. The older and larger one, 33 metres See also:long, 24 M. deep, 16 m. high, contains on the ground See also:floor the aquarium, which is open to the public. On the first floor there is, facing See also:south, the See also:principal library, ornamented with See also:fresco paintings, and, facing See also:north, a large See also: The ground floor of the smaller See also:building, which was finished in 1887, contains the rooms in which the animals are delivered", sorted and pre-served, and the fishing tackle kept, together with the workshop of the engineer; on the first and second floors are workrooms, amongst others the botanical laboratory; on the third floor are See also:store-rooms. In the See also:basement of both buildings, which is continued underneath the See also:court, there are sea-See also:water cisterns and filters, engines and store-rooms. The materials for study which the station offers to the biologist are specimens of marine animals and See also:plants which abound in the western See also:part of the Mediterranean, and especially in the Gulf of Naples. To obtain these, two See also:screw-steamers and several See also:rowing boats are required, which are moored in the See also:harbour of Mergellina, situated See also:close by. The larger steamer, ` Johannes See also: The principal appliances for study with which the station provides the biologist are workrooms furnished with the apparatus and chemicals necessary for anatomical research and physiological experiments and tanks. Every student receives a tank for his own See also:special use. The large tanks of the principal aquarium are also at his disposal for purposes of observation and experiment if necessary. "The water in the tanks is kept fresh by continual circulation, and is thus charged with the See also:oxygen necessary to the See also:life of the organisms. It is not pumped into the tanks directly from the sea, but from three large cisterns (containing 300 cubic metres), to which it again returns from the tanks. The water wasted or evaporated during this See also:process is replaced by new water pumped into the cisterns directly from the sea. The water flows from the large cisterns into a smaller cistern, from which it is distributed by means of an electric See also:pump through vulcanite or See also:lead pipes to the various tanks. The water with which the tanks on the upper floors are filled is first pumped into large wooden tanks placed beneath the roof, thence it flows, under almost See also:constant pressure, into the tanks. The water circulated in this manner contains by far the largest number of such animals as are capable of living in captivity in See also:good See also:condition. Some of them even increase at an undesirable See also:rate, and it some-times happens that See also:young Mytilus or Ciona stop up the pipes; in laying these, therefore, due regard must be had to the arrangements for cleaning. For the cultivation of very delicate animals it is necessary to keep the water absolutely See also:free from harmful bacteria; for this purpose large See also:sand-filters have lately been. placed in the See also:system, through which the water passes after leaving the cisterns. Each of the smaller cisterns, which are fixed in the workrooms, consist of two water-tanks, placed one above the other; their frames are of wrought See also:iron and the walls generally of See also:glass. Vessels containing See also:minute animals can be placed between these two tanks, receiving their water through a See also:siphon from the upper tank; the water afterwards flows away into the See also:lower tank.
" The twenty-six tanks of the public aquarium (the largest of which contains 112 cubic metres of water) have See also: The station also publishes a Zoologischer Jahresbericht, which at first treated of the entire See also: Of the two methods hitherto in use, that of pumping a See also:jet of air into tanks otherwise stagnant or nearly so (See also:Brighton), while supplying sufficient oxygen, has so many other disadvantages, that it has not been employed regularly in any of the more modem aquaria. It is, however, still useful in aerating quite small bodies of water in which See also:hardy and minute organisms can be isolated and kept under See also:control. In the other method, now in See also:general use, a fine jet of water under pressure falls on to the surface of the tank; this carries down with it a more than sufficient air-supply, See also:analysis showing in some cases a higher percentage of oxygen in aquarium water than in the open sea. The water supply is best effected by gravity from reservoirs placed above the tanks, but may be also achieved by See also:direct pumping from See also:low reservoirs or from the sea to the tanks. Provided that an unlimited supply of pure water can be obtained cheaply, the overflow from the tanks is best run to See also:waste; but in aquaria less fortunately placed, it returns to a storage low-level reservoir, from which it is again pumped, thus circulating See also:round and round (Naples, Plymouth). The storage reservoirs should be in all cases very large in comparison with the bulk of water in circulation; if practicable, they should be excavated in See also:rock, and lined with the best See also:cement. There is no See also:reason why they should not be shallow, exposed to See also:light and air, and cultivated as rock-pools by the introduction of seaweeds and small animals, but they must then be screened from See also:rain,. See also:cold and dust. The pumps used in circulation will be less likely to kill minute animals if of the plunger or See also:ram type, rather than rotary, and should be of See also:gun-See also:metal- or one of the new See also:bronze-See also:alloys which take a See also:patina in See also:salt water. For the circulating pipes many materials have been tried. Vulcanite is not only expensive and brittle, but has other disadvantages; See also:common iron pies, coated internally with cement or See also:asphalt or glazed internally, with all unions and See also:joints cemented, have been used with more or less success. Probably best of all is common lead piping, the joints being served with red-lead; water should be circulated through such pipes till they become coated with in-soluble carbonate, for some time before animals are put into the tanks. For small installations glass may be used, the joints being made with marine See also:glue or other suitable cement. In building the tanks themselves, regard must be had to their special purposes. If intended for show-tanks for popular admiration, or for the study of large animals, they must be large with a See also:plate-glass front; for See also:ordinary scientific work small tanks with all sides opaque are preferable from every point of view. According to their character, size and position, fixed tanks may be of See also:brickwork, See also:masonry or rock, coated in each See also:case with cement; asphalting the sides offers no particular advantages, and often gives rise to great trouble and expense. All materials, and especially the cements, must be of the finest quality procurable. For smaller and movable tanks, See also:slate slabs bolted or screwed together have some disadvantages, notably those of expense, See also:weight and brittleness, but are often used. Better, cheaper and lighter, if less permanent, are tanks of See also:wood bolted together, pitched internally. Glass See also:bell-jars, useful in particular cases, should generally have their sides darkened, except when required for observation. See also:Provision should always be made for cleaning every part of the tanks, pipes and reservoirs; all rock-work in tanks should therefore be removable. As regards the See also:lighting of fixed tanks, it should always be directly from above. In all tanks with glass sides, whether large or small, as much light as possible should be kept from entering through the glass; otherwise, with a side-light, many animals become restless, and See also:wear themselves out against the glass, affected by even so little light as comes through an opposite tank. In cases where distance from the sea or other causes make it impracticable to allow the overflow from the tanks to run to waste, special precautions must be taken to keep the water pure. Chemically speaking, the See also:chief character of the water in an aquarium circulation, when compared with that of the open sea, lies in the excessive quantity of See also:nitrogen present in various forms, and the reduced alkalinity; these two being probably connected. The excess of nitrogen is referable to dead animals, to waste food and to the excreta of the living organisms. The first two of these See also:sources of contamination may be reduced by care and cleanliness, and by the See also:maintenance of a flow of water sufficient to prevent the excessive See also:accumulation of sediment in the tanks. The following experiment shows the rapid rise of nitrogen if unchecked. A tank with a considerable fauna was isolated from the general circulation and aerated by four air-jets, except during See also:hours 124—166 bf the experiment; See also:column I. shows per See also:Ioo,000 the nitrogen estimated as See also:ammonia, column II. the See also:total inorganic nitrogen: I. II. Sea-water at source of original 0.003 supply . 0.001 Aquarium water in tank at com- 0.400 mencement of experiment . 0.012 After 221 hours . 0.020 . 11 75 0.025 I.200 11 93 „ 0.019 . 1211 „ 0.012 11 141 „ . 0.015 2.200 165 0.025 .. 169 „ . 0.025 11 189 . .0.012 During this time the alkalinity was reduced to the See also:equivalent of 30 mg. CaCO3 per litre, ocean water having an alkalinity equivalent to 50-55 mg. per litre. It has been suggested that the organic nitrogen becomes oxidized into nitrous, then into nitric See also:acid, which lowers the carbonate values. A great See also:deal of reduction of this nitrogenous contamination can be effected by filtration, See also:AQUAVIVA 239 a method first introduced successfully at Hamburg, where a most thriving aquarium has been maintained by the See also:local Zoological Society for many years on the circulation principle, new water being added only to compensate for waste and evaporation. The filters consist of open See also:double boxes, the inner having a bottom of perforated slate on which rests rough See also:gravel; on the latter is fine gravel, then coarse, and finally fine sand. Filtration may be either upwards or downwards through the inner See also:box to the See also:outer. Such filters, intercalated between tanks and reservoir, have been shown by analysis to stop a very large proportion of nitrogenous See also:matter. It is doubtful whether aquarium water will not always show an excess of nitrogenous compounds, but they must be kept down in every way possible. In small tanks, well lighted, seaweeds can be got to flourish in a way that has not been found practicable in large tanks with a circulation; these, with Lamellibranchs and small See also:Crustacea as scavengers, will be found useful in this connexion. Slight or occasional circulation should be employed here also, to remove the film of dust and other matters, which otherwise covers the surface of the water and prevents due oxygenation. In such small tanks for domestic use the fauna must be practically limited to bottom-living animals, but for purposes of research it is often desired to keep alive larval and other surface-See also:swimming animals (plankton). In this case a further difficulty is presented, that of helping to suspend the animals in the water, and thus to avoid the exhaustion and See also:death which soon follow their unaided efforts to keep off the bottom; this See also:duty is effected in nature by specific gravity,, See also:tide and surface current. In See also:order to deal with this difficulty a See also:simple but efficient apparatus has been devised by Mr E. T. See also: Additional information and CommentsThere are no comments yet for this article.
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