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A freshwater aquarium may be planned in two different ways, through either an ornamental or a natural approach. Konrad lorenz, one of the founders of ethology, has forcefully argued in favor of the natural type of freshwater aquarium, on the ground that it reproduces, as nearly as is possible, a natural environment tending toward biological equilibrium. But such aquaria are often not aesthetically ideal and are relevant only to natural-science studies.
Contrary to popular belief, neither freshwater nor marine aquaria constitute "samples" of natural environments transplanted into our homes. An aquarium, and in particular a marine aquarium, is an abnormal environment whose success depends largely on whether the animals are able to adapt to such different conditions. If the animals survive, we should congratulate them rather than ourselves, because they are more likely to have done so in spite of, rather than beccause of, us.
The aquarium environment is undoubtedly anomalous in that it is isolated from the beneficial effects of exchanges with the biosphere, and some of its biological parameters are very different from the natural ones.
In spite of these difficulties, however, it is quite
possible to keep a large number of aquatic animals in captivity. To do this, you
must above all learn to detect deteriorating environmental conditions and
correct them before they become irreversible. The principles to follow,
therefore, derive from an understanding of the mechanisms at work in an aquarium
and the realization that aquatic animals have very specific, basic physiological
requirements which make them, so to speak, physiological extensions of the water
they live in. Bearing this in mind, and with some practical experience, you will
find owning an aquarium can be very satisfying.
Although frame tanks are economically attractive, they are considered obsolete, particularly for use in marine aquaria. By a frame tank we mean the very common type with a metal framework (or, more rarely, a plastic one) and glass walls sealed with putty. Even if accurately built, a tank of this type is rapidly corroded by seawater and should therefore contain only fresh water. The frame is usually made of enameled iron, a light alloy or stainless steel, but is always subject to corrosion and, moreover, liberates toxic substances into the water. Plesiglas tanks also liberate small amounts of toxic substances but are aesthetically very pleasing. This type of container, even if it is built of high-quality materials, has drawbacks. Plexiglas is not particularly hard, so it scratches easily an tends to lose its clarity. It also tends to yellow with time.
Thus the best aquaria are those built entirely of glass and banded by silicone adhesives, which afford very resilient joints and yet retain some degree of elasticity. For very large tanks you can also use Eternit walls and a glass front. The Eternit surfaces in contact with water should be carefully painted with nontoxic paint and thoroughly washed in running water before the aquarium is used.
An important factor to take into account in acquiring
or building a tank is the thickness of the glass. For a sidewall 40 in (1 m)
high, the glass must be at least 1\2 in (13mm) thick, while the bottom must be
at least 1\2-3\4 in (13-19 mm) thick. You also need to keep in mind the overall
weight of the tank and give careful thought to its location.
Fresh water contains small amounts of salts and gases in solution. Other substances, such as acids, may also be present in smaller quantities. With the aid of devices that measure electrical conductivity, fresh water may be classed as "hard" or "soft" according to the sodium and calcium it contains in compounds.
Freshwater fishes may prefer soft, hard or even
slightly bracish water. In the first case, spring, well or tap water (if free of
chlorine) is adequate. To obtain softer water it is sufficient to add a
proportion of distilled water, whereas the addition of sea salts (measured with
a hydrometer) yields brackish water. Rainwater should not be used, because it
contains man-made atmospheric pollutants. Acid water, which some species need in
order to reproduce, is distinguished by its amber color. It is obtained through
the use of peat soils, long-submerged wood or chemical additives, such as tannic
acid.
Seawater differs from fresh water by its salt content, generally between 2 and 4 parts per thousand. This variability in salt content is very important. You must keep the salinity in the aquarium as close as possible to that which exists in the natural environment of its inhabitants. At first glance, it may seem that seawater itself would be best for aquarium use, but because of its pollution and tendency to deteriorate, it is usually safer to use appropriately condition "synthetic" seawater. Natural seawater is a "living" substance, containing living organisms with which it interacts. Many commercially available sea-salt preparations will adequately sustain marine life. They also contain those trace elements which, present in low concentrations, are essential to many biological functions. Because these trace elements are consumed, half or a third of the water should be changed every three weeks. Unlike recently collected seawater, which usually contains too many6 bacteria, artificial seawater does not contain enough, which is its main drawback. This can be corrected by conditioning, according to the following procedure.
The salt mixture should be dissolved in a clean
container and the mixture should be aerated for 48 hours. After the water has
been allowed to settle for at least a week, soil or filtered solids from an
established aquarium should be added. A technique to accelerate conditioning is
to introduce highly resistant organisms that liberate organic substances and
ammonia into freshly made-up water, thereby mineralizing and nitrifying the
water.
Alkalinity is an important variable in both fresh and sea water. It is expressed in pH units (hydrogen-ion concentration on a logarithmic scale). Neutral water has a pH of 7, with alkalinity above and acidity below. Apart from some particular species with unusual reproductive needs, freshwater fishes can live in pH values of 6.5 ti 7.5.
Natural seawater usually has a pH value between 7.9 and
8.5 and is thus slightly alkaline. In the aquarium, the pH value of artificial
seawater should be kept between 7.5 and 9.5. The optimal range for fishes lies
between 7.5 and 8.3. Freshly prepared seawater has a pH value of between 7.5 and
7.7, but after a few days it tends to reach values above 8. It is essential to
monitor the pH value. Commercially available indicator papers come with
instructions for use. If the pH value is too low (the water is acid), one can
raise it by adding sodium bicarbonate (NaHCO3
) or other alkalinity
correctors for aquarium use. If, on the other hand, the pH value exceeds the
upper limit (8.6 for seawater, which is thus alkaline), one should add potassium
dihydrogen orthophospahte (KH2
PO4). Limestone shingle or sand, which contains calcium and magnesium
carbonates, has an efficient buffering effectg and stabilizes the pH value.
Living organisms in an aquarium excrete metabolic wastes (urine and feces) and soluble proteins (largely albumins) derived from decaying food. These lead to the accumulation of highly toxic nitrogen compounds such as ammonia, which must be oxidized to nitrates by bacteria. Nitrates, in low concentrations, are essential to the conditioning of water and are particularly important as plant nutrients. (nitrate concentrations of 100 mg/I should be considered excessive, although organisms are able to adapt to gradual increases of up to ten times this amount.) Frequent water renewal and efficient filtration with large centrifugal pumps are sufficient to keep nitrate levels under control. Marine aquaria, in particular those with large numbers of animals, should contain an absorption column with a foamer, to eliminate soluble proteins before they form toxic nitrogenous compounds.
Apart from certain bacteria, all aquatic organisms are aerobic and thus need oxygen dissolved in water for respiration. It is therefore essential for the water in aquaria to contain a high proportion of dissolved oxygen, particularly if the water temperature is high, as in tropical aquaria; this is because the solubility of oxygen in water is inversely proportional to the temperature.
A pump, therefore, is needed to aerate aquarium water. It may be either a membrane pump or, better still, a piston one. The pump will constantly blow air through a diffuser (natural or synthetic) connected to it by a tube made of silicone or a chemically inert plastic. The pump should be silent and, of course, extremely reliable, functioning continuously without breaking down. The diffuser, or porous stone, should have pores of a diameter small enough to increase the surface area in contact with water without requiring excessive pump pressure.
If a centrifugal pump is used for filtration, a venturi tube connected to the water-return tube will blow in a good deal of aif. Although most aquatic animals prefer still or slightly moving water, some prefer rather more turbulent water; this is another function of a vigorous airstreams. The movement of the water will also tend to increase gaseous exchange with the atmosphere and will help to bring the oxygen content closer to its optimum concentration of 50 percent. Pumping, however, will also dissolve atmospheric pollutants in the water. To avoid this increasingly bothersome drawback, it is best to prefilter the air entering the pump by bubbling it through a small volume of water, which will absorb most toxic airborne substances.
For an aquarium to function well, the filter is crucial, because it retains suspended particles and decaying foodstuffs. The filter system should be as large and efficient as possible. Internal filters are impractical and not particularly efficient and are not recommended. External filters with centrifugal pumps are preferred. These have very high rates of flow and ensure continuous mixing of aquarium water.
Ideally, the output of a filter system should be enough to ensure a complete recycling of the water every one or two hours. The filtering material removes unwanted substances from the water. Nylon wool acts as a mechanical filter and retains all the particles that come into contact with it. Activated charcoal acts as both a mechanical and a chemical filter, thanks to its ability to absorb a wide variety of toxic substances. Pumice or marble chips are also of great use in a filter. Pumice chips release trace elements, while marble acts as a pH buffer. Anion-exchange resins are of doubtful value. They remove soluble protein degradation products and seem useful at first sight; their defect lies in their ability to bind trace elements and thus impoverish the water.
For these reasons, it is best to install a foamer or protein skimmer in marine aquaria. This device is made more efficient when it is combined with an ozone generator and works by absorbing in a special column a foam containing a high proportion of proteins and other wastes. The wastes are gathered in a small container and may then be easily removed. It must be remembered that all drastic systems of filtering and purification should be used sporadically, and that only traditional filters are meant for continuous use. An albumin foamer should be used only as an emergency measure. All filter materials are short-lived and should be changed frequently. The filter system should be dismantled and the nylon wool replaced regularly --- more often than is usually recommended by the makers. Mixed filtering is at present very popular; it includes both an external filter and one or more easily maintained internal filters. The latter are held by special partitions on the side or back surface of the aquarium. More elaborate systems include a biological filtering compartment containing algae and bacteria. Filter-feeding mollusks may also contribute to the removal of bacteria and suspended particles.
Aquatic animals from cold or temperate climates cannot tolerate a plunge into temperatures higher than those in their normal habitat. However, they may be made to adapt, within limits, to higher temperatures by means of a gradual increase in the temperature of 1-2 degree Fahrenheit (5-1 degree centigrade) per 24 hours. Mediterranean and cold-sea animals do not tolerate temperatures above 72 degree Fahrenheit (22 degree centigrade), whereas tropical animals usually prefer temperatures between 75 and 83 degree Fahrenheit (24-28 degree centigrade) and show signs of discomfort below 68 degree Fahrenheit (20 degree centigrade). Water is usually heated by a glass tube containing an electrical heating element, whose power output is expressed in watts. In spite of the rule of thumb of 100 litre, it is best to include a thermostat in the heating system. This will switch the heating current on and off to maintain the selected temperature.
Temperature readings should be obtained from a thermometer situated as far as possible from the heater. Mercury and thermocouple thermometers are the most precise, but the cheaper alcohol type is adequate. The thermometer should be out of reach of aquarium animals, particularly of large fish and crustaceans, or protected in such a way as to make its glass parts inaccessible. A broken thermometer, especially of the mercury type, could rapidly poison the water. To obtain uniform heating, it is best to suspend the heater in a water current and to avoid setting it on the bottom or burying it.
Cold-water flora and fauna suffer from high summer temperatures and require special care. They must be kept in a cool, well-ventilated environment away from direct sunlight. If this is not sufficient to keep the temperature below 68 - 72 degree fahrenhite (20-22 degree centigrate) one can use a spiral glass pipe immersed in the aquarium, connected by tubes to the water pipe and the drain. It is possible to use thermostatically controlled filter-pump refrigeration units, but these are expensive. Water temperature is an essential factor in aquarium life. Since its control must be scrupulously maintained, under normal comditions and particularly in emergencies, you should buy the most effficient equipment you can afford.
All living organisms, animals as well as plants, require a certain amount of light and a light - dark cycly. But putting the aquarium next to a window in order to expose it to natural light - dark variations is not recommended. The levels of indirect natural light are usually not sufficient, and excessive direct sunlight will raise the water temperature. Aquaria should be illuminated with artificial lights that are carefully isolated electrically from the water. Ordinary incandescent bulbs are inefficient and ill suited to the job, because of their inadequate light spectrum and their undesirable heat. Fluorescent tubes, on the other hand, are highly recommended; they are both very efficient and available in a wide ranghe of colors that can be matched with the aquarium environment. Particularly efficient and available in a wide range of colors that can be matched with the aquarium environment. Particularly efficient fluorescent tubes, designed to replace natural lighting completely, are commercially available. At least one of these should be used to provide the quality and quantity of light needed by most living things.
The light - dark cycle must be accurately determined, because an excessively long light period may cause the rapid growth of encrusting algae. Depending on the power of the available light sources, it is best to alternate ten hours of light with fourteen hours of darkness, gradually modifying these values to minimize algal growth. The use of ultraviolet lights is often recommended. These, if used with very great caution, kill bacteria and widen the light spectrum in the aquarium. Aquarium water, especially seawater, tends to become turbid as a result to uncontrolled bacterial growth. In such a case, an ultraviolet source solves the problem in a few hours. Furthermore, ultraviolet light has beneficial effects on both the prevention and the cure of certain skin deseases of fishes.
A number of frequently used accessories are necessary for daily aquarium maintenance. Mention has already been made of the need to install a thermometer. Aquarium thermometers are often low - precision industrial products, and it is a good idea to use a precision, rapid - reading thermometer for occasional checks.
Marine aquaria require a hydrometer to determine water density, which is related to salt content. Under normal conditions, pure water weighs between 1.024 and 1.029 kg/l. On the hydrometer scale these values are marked respectively as 1024 and 1029. Control of density and salinity is necessary because evaporation, proportional to temperature, tends to increase the salt concentration. Fresh water may be added to reestablish normal salinity.
The pairs of stainless steel or plastic forceps, one long and one short, will enable you to pick up objects from the bottom, move the fittings, introduce food for sessile organisms, place plants, etc. To capture aquarium animals, you need several fishnets of various sizes. To clean the algae and dirt from internal surfaces of the aquarium you can use a blede scraper, making sure not to scratch the glass, or a pair of flat magnets covered with synthetic abrasive on one face. These can be bought or made. One magnet is placed on the inside of the glass, while the other one,covered in felt, is placed opposite, with its poles reversed, on the outside. If the external one is moved, the abrasive magnet will follow it, thereby cleaning the glass without damaging it.
There are two reasons why aquatic animals should never be touched with the hands. 1) The mucous layer with which fishes in particular are covered is vital to their well-being. Damage to this protective coat can lead to a higher incidence of disease. 2) Many organisms are dangerous to the handler, either because they have mechanical means of defense, such as crustacean claws, or because they bear venomous spines (certain species of fish) or stings or sharp jaws, as is the case with sea anemones and certain annelids.
Aquarium maintenance operations include periodic water changes and the removal of waste materials from the bottom. A siphon made from a length of glass or plastic tubing, connected to a rubber tube, can be used in both cases. To extract sediments, you can connect the tube to the pump of the external filter, if there is one, and thoroughly sweep the aquarium with the open end of the aspirator tube. So-called rapid filters are also available and can be used in emergencies or to siphon out sediments and clear the water. Some suppliers of scientific instruments also offer filter cartridges, usually rather expensive, which collect algae and even bacteria.
Pipes, corners and tubing are best cleaned with bottle brushes, particularly the type with a long flexible handle, which is well suited to aquarium use. The various types of food dispensers (floating rings, floating sieves for Tubifex, etc.) are usesul, if sufficiently numerous, to avoid unnecessary and damaging competition among animals at feeding time.
Once all the aquarium components and accessories are collected, you are ready to assemble and equip the aquarium. One of the most exciting things about aquaria is that, apart from some general rules, each aquarium has a character of its own and reflects the preferences of its owner. However, it is always necessary to keep in mind the physiological needs of aquarium fauna and flora from both an aesthetic and a biological standpoint. As far as possible, you should look upon an aquarium as a model environment, with all the components of a natural habitat.
The preparation of a freshwater aquarium begins with the installation of the substrate. This may be made from various materials - for example, sand or pebbles - which may be bought or collected in natural surroundings. In the latter case, you must make sure that the material comes from unpolluted areas, and in any event it should be washed thoroughly with running water before use. The substrate is then spread on the aquarium floor, sloping gently from a depth of 2 1/2--4 in (6--10 cm) at the back wall to 2 in (5cm) or less at the front, this makes it easier to plant a lot of vegetation at the back of tank, to creat a denser backdrop.
After putting in approximately half the total water, you can add stones, rocks and wooden structures. Stones and rocks should be insoluble, so that they will not liberate potentially toxic salts which would give rise to a chemical imbalance. Strikingly attractive wooden objects can be made from roots, branches, small stumps, etc.; but make sure you use tough, durable wood. Pieces of wood found in water (peat-bog wood, for example) are recommended. These can be bought in special shops. Some wooden ornaments may slightly color and acidify the water, which is usually undesirable but is sometimes favorable to the survival and reproduction of certain species. When you are in doubt as to the quality of the wood, it is best to wash it in running water and boil it in water for two hours berore putting it into the aquarium.
If the aquarium is to contain animals that need to leave the water at least temporarily (such as certain fishes, crustaceans, amphibians and reptiles), it is best to build easily accessible structures abovewater. For the installation of plants, which will draw nutrients from food particles and waste products released by the animals, you may use earthenware pots buried in the soil or you may put them directly into the soil itself, making sure to plant them with a short lateral movement rather than simply by pushing them in vertically. This ensures correct positioning of the roots.
Freshwater aquaria lend themselves to a great variety of ecologies, while seawater aquaria aquaria are of two main types: temperate(e.g., Mediterranean) and tropical (e.g.,coral reef).
The temperate marine aquarium should have a mixture of sand and stones to provide for the needs of animals living on a soft bottom (sand,mud) and of those which prefer rocky substrates with cavities and cracks. To avoid stagnation of water in the substrate it is best to use medium-grained sand (particle size not smaller than 1/16 in or 1-1.5mm). Avoid fine sand, which is likely to reach the filter system whem stirred by the animals.In contrast to the fresh water aquarium, the sand-bottomed marine aquarium requires a thicker substrate of up to 6-8 in (1-2 cm). You can distribute the sand in steps, higher at the back of the tank, and keep it in place by flat stone dikes. To facilitate water renewal in the soil, it is best to include some mollusk and coral fragments in the sand. This alone is not sufficient, however, and the water must be filtered every week, while the sand is moved to stir up the particles trapped in it. Shell fragments also tend to stabilize the alkilinity level.
"Living rocks" are of great value in both temperate and tropical seawater aquaria: not only are they beautiful to look at, but they also condition the water. These living rocks are natural rocky fragments inhabited by various plants and animals including algae, annelids, crustaceans and mollusks. These organisms present drawbacks as well as advantages, because they are fragile, as in most balanced biological systems. They may die suddenly without apparent reason, and they do not tolerate foreign substances such as drugs in the aquarium water. To reconstruct a coral environment, one usually adds the chalky skeletons of branched corals, particularly white or red, and some attractive gorgonian skeletons. The possibilities of arranging them with stones and rocks are infinite. However, it is best to ensure that tall structures are stable by resting them as solidly as possible on the tank floor or, if necessary, by using nontoxic adhesives to join them together. Such arrangements are usually taller at the back of the aquarium, to prevent them from looking out of proportion. You can also make use of several tricks to simulate seawater depths, such as painting the outside surgace of the back of the aquarium or, if necessary, adding glass or plastic panels of the desired color inside.
Like all objects that are to be introduced into an aquarium, coral skeletons should be thoroughly washed before use. Unfortunately, the appearance of these natural materials tends to deteriorate rather rapidly underwater. Their porosity gives them a tendency to retain suspended particles from the water and to become and to become coated with brown and green algae. They therefore require periodic cleaning, including energetic brushing in running water, immersion in boiling water for at least three hours, and about five days' immersion in concentrated seawater. An equally effective method -- slower, but rather less laborious -- is immersion in a 15-percent solution of potassium hydroxide for a week, after which the coral must be washed in running water for at least ten days. Its chalky composition precludes the use of hydrochloric acid, even in low concentrations, because it would make them extremely fragile or destroy them outright by dissolving them.
To summarize, then, the rules of assembly and furnishing : it is best to give this part of the construction a good deal of thought and to build carefully and slowly, experimenting with various arrangements and their maintenance needs. As for the number of animals to be kept in an aquarium, this corresponds to the volume of water. It is best to keep furnishings functional and avoid using so many as to clutter the tank. Few animals and simple furnishings usually result in fewer disappointments for beginners. The various plastic objects available hve purposely not been mentioned; they are chemically inert, but their use is a question of personal taste. They certainly do not make the aquarium a natural environment.
Maintaining an aquarium, whether freshwater or marine, requires certain precautions to avoid damaging the fittings and equipment. This is particularly true with marine aquaria. For example, we have already mentioned the importance of using a net to capture or restrict an animal without directly touching it. If hand contact is unavoidable, it is best to wear high-quality rubber gloves to protect both you and the aquarium animal. Fish scales are covered with skin and mucous layers of varying thickness necessary both for osmotic exchange and for protection from pathogens (bacteria, fungi, etc.) ever present in the water. This barrier must not be impaired. Other animals have delicate, fragile structures that are easily damaged if handled without extreme care. In addition, there is the risk to the handler from many organisms' defensive and offensive structures. Besides having claws and spines that can inflict simple wounds, many aquatic, and in particular marine, animals are venomous.
A list of noxious animals would draw on all major groups listed in zoological textbooks. The aquarium owner must beware of coelenterates (jellyfish, sea anemones and living corals), annelids (burrowing or free-living marine worms), mollusks (some cones and cephalopods are notorious for their toxicity), crustaceans (medium and large crabs and prawns), echinoderms (sea urchins and starfish) and fishes (scorpion fishes and others). Not all animals belonging to these groups are venomous, but some secrete extremely potent poisons which may be fatal to humans. With such animals it is best to act prudently, but without excessive fear, keeping in mind that these dangerous devices are used to ensure survival in hostile natural environments.
It us also important to remember the presence of electricity in or near aquaria, and that water (particularly salt water) and electricity should be kept well insulated from each other. In the first place, water attacks all materials, and electrical appliances may become poorly insulated; secondly, salt water conducts electricity well and enables electrical leaks to occur. In marine aquaria, therefore, it is best to prevent accumulation of salt deposits by periodically, after disconnecting the power, washing the appliances in fresh water and drying them thoroughly. ALWAYS REMEMBER WHEN HANDLING ANY ELECTRICAL APPLIANCES: PULL OUT ALL PLUGS FROM THEIR SOCKETS. Turning off the switch is not enough; switches can fail to interrupt the flow of current.
Similarly, except when adjusting the thermostat, you should disconnect the power when dealing with lights and heaters. You should also periodically check the state of insulating materials -- particularly plastic and rubber parts, which age rather rapidly; they should be replaced at the first sign of deterioration. When installing electrical appliances, you should strictly follow the maker's instructions and avoid submersing parts not designed for underwater use. Current leaks, often the first sign of an electrical fault, can be detected with a voltmeter. If any leaks are found, the electrical equipment should be thoroughly tested. One final rule concerning immersion heaters: do not switch them on outside water, and do not immerse them once hot; if you do, they may explode. Sudden temperature jumps are damaging to plants and animals, and also can fracture glass tanks. For this reason, when filling or washing the tank, make sure that the water added is at the same temperature as the tank water, or ambient temperature. In any event, very hot or very cold water should never be added.
No living organism can survive without a constant energy input in the form of food. Plants make use of light energy to transform inorganic compounds and constituents into organic ones by means of photosynthesis. They draw their nourishment from the soil and the water.
An aquarium will be able to support plant life after it has been inhabited by animals for some time, but it is possible to shorten this period by adding fertilizers or special soils such as peat, which releases humic acids into the water. Animals pose more complex feeding problems. They may be roughly subdivided into dietary categories according to ecological criteria: herbivorous animals, whose diet is almost exclusively composed of plants; carnivorous ones, which eat other animals; omnivorous animals, which combine both the above, and scavengers (detritus feeders), which feed on decayed material in suspension and on the bottom, and on organic wastes of various types.
These varieties of animals also have different feeding rhythms; carnivorous predators feed sporadically, while all the others feed more or less continuously during their diurnal or nocturnal activity periods. Feeding times, as well as the type and quantity of food, will depend on the nature of the aquarium fauna. The best compromise usually consists of frequently adding small amounts of food sufficient to feed all the animals without leaving any food floating, suspended or on the bottom. This principle also holds for animals needing specific diets.
If the aquarium contains predators, and if problems of compatibility arise, the predators must be fed live prey or adequate substitutes, following the rhythms suggested by the species natural habits. Providing excess food inevitably leads to deterioration of the delicate environmental balance and of the health of its inhabitants. On the other hand, although aquatic animals will tolerate extremely long fasts, one should not go to the opposite extreme and provide too little food. It is easy to reach a satisfactory feeding pattern for any aquarium, provided that competition, present in nature and emphasized by artificial aquarium conditions, is taken into account. Food should be spread uniformly across the aquarium in order to favor those animals which are somehow unable to compete with animals better or more rapidly adapted to the aquarium.
A wide variety of food for freshwater animals is available, all more or less adequate if the diet is supplemented with fresh, natural food. Freeze-dried foods are convenient and well tolerated. Among these are brine shrimps, Daphnia and other crustaceans, Tubifex, fish eggs and meat (liver, heart, etc.). A short list of natural foods, many of which are easily found in natural surroundings or in special shops, includes living plank tonic animals (brine shrimps, Daphnia and other crustaceans), Tubifex and other worms, small mollusks, insect larvae and small adult insects, small fish and various vegetables (boiled rice, fresh or boiled vegetables, etc.).
In particular, young fishes (larvae and older fry) require specially prepared products, or even better, protozoan cultures (Paramecium) and plankton (Artemia nauplii); but bear in mind that larvae of oviparous fishes need smaller particles than larvae of viviparous species. Marine organisms have diets similar to freshwater ones, with the addition of fresh or frozen mollusks and crustaceans, chopped or liquefied fish and algae. Liquefied foods prepared with mortars or blenders are particularly suitable for certain coelenterates (sea anemones, gorgonians, branched corals and other corals) and for so-caled filter feeders (bivalves, many crustaceans, etc.). To make the best use of frozen foods, divide them into portions and wrap each one in aluminum foil. In this way it is possible to use food as it is needed while conserving the rest in good condition.
Plankton is available in the form of Artemia salina; this is a small crustacean which lives in very salty waters such as salt marshes and flats that are subject to high evaporation. The small brown eggs of these crustaceans hatch better if exposed to a temperature of 77 degree F (25 degree C) for one hour and ten immersed in well-aerated seawater (artificial or natural), at 77 degree F (25 degree C) in a shallow container. Depending on the temperature, salinity and illumination, Artemia larvae, known as nauplii, hatch within 12 to 20 hours and swim vigorously, using their three pairs of swimming legs. Excellent Artemia incubators are available and will facilitate these processes. If most of the container is shielded area and can be easily removed with a fine-meshed dipnet.
A good appetite and eagerness to feed are signs of good health and adaptation to environmental conditions. Recently acquired animals, however, seem unwilling to feed even if the food is varied. The change from a natural habitat or a commercial aquarium to the new environment often requires a long period of adaptation. Various animals, including many fishes, do not find aquarium food palatable. These animals may require painstaking adaptation periods while their diet is gradually shifted from the natural one, which may be difficult to find, to imitate or even to ascertain, to artificial ones, Fortunately, however, this is unusual, because animals bought from reliable dealers have already been adapted to aquarium life. One final point: natural foods may carry undesirable contaminants or organisms and should be washed in running water before use.
Quarantine refers to the set of hygienic precautions designed to prevent a newly arrived animal from infecting or infesting those already living in the aquarium. This usually applies to fishes that often carry in their natural state various diseases or pathogens as well as ecto - and end parasites. Although there are specific regulation. governing the import, transport and sale of animals, the more reputable dealers apply supplementary measures to observe and disinfect animals that are going to be sold.
These rules, however, are not always respected, and the aquarium owner should have a spare tank specifically designed for the quarantine of newly arrived animals. This glass tank, which can also be used for the treatment of diseased fishes, should contain 6 1/2 - 11 gallons (30-50 liters) of water. It should be sparsely furnished with a pebble substrate and an earthenware pot resting on its side to provide a refuge for the animal during maintenance. Tropical animals will, of course, require safe, thermostatically controlled heating as well as efficient filtration and aeration.
The quarantine procedure for recently imported tropical fishes is as follows. Bring the temperature of the water up to 85 - 86 degree F (29 -30 degree C) and keep the fish under observation for two weeks. The high temperature causes latent diseases to emerge. If no symptoms have appeared after this time, gradually lower the temperature to 77 degree F (25 degree C) and keep the fish under observation for another week.
The mild disinfectants that manufacturers suggest for use in the second phase are certainly not damaging, but they are of dubious value to a healthy animal. On the other hand, one may treat the animals with antibiotics for eight hours (never more, for reasons of toxicity, than ten hours). With the filter pump switched off and increased aeration, add 200,000 international Units of penicillin per liter of water before introducing the animal into the tank. The animal must be kept under observation and transferred to clean water if it appears not to tolerate the drug and exhibits anomalous behavior.
Quarantine methods, which are the subject of a great deal of disagreement, may also include the use of drugs specifically designed for aquarium use. This, however, does not eliminate the need to adapt the animal to captivity and, above all, to aquarium food. In order to make this phase as quick and easy as possible, several forms of sedative treatment are now being developed to reduce the stresses experienced by the more emotional types of animals. When quarantine is completed, you can transfer the animals to the aquarium without any further fears about hygiene.
The Meaning of Color Variations in Fishes,
Temporary or seasonal color variations are rather common in animals and serve various adaptive purposes. They are related to physiological variations (such as reproductive periods, particularly in males) or psychological states (changes of "mood"), or may serve to render the animal less conspicuous.
It is well known that the males of many species exhibit a "nuptial display" with brilliant, more intense colors, sometimes different from the normal ones. Less well known is the ability of certain types of fishes to change their color patterns with their mood, as in the case of the well-studied cichlids. Indeed, some animals have as many as ten different color displays, depending on whether they are quiet, anxious, frightened, socially dominant or submissive, defending their territory, etc. On the other hand, some fishes such as the soles change their environment. The butterfly fishes and other species also vary their patterns according to age, so that variations of color quality and distribution are found withina species, sometimes to such an extent that they are mistaken for separate species.
The structures responsible for these color changes are known as chromatophores), yellow (xanthophores), red (erythrophores), white (leucophores) or iridescent (iridocytes). The chromatophores are under hormonal and nervous control and when stimulated may either contract or expand the pigment granules they contain, giving rise to paler or more intense coloring.
Animals must be suitably transported when taken from their natural environment and when bought from a dealer. Small, square-bottomed Plexiglas aquaria equipped with battery-operated pumps were once popular, but plastic bags are now preferred for practical reasons of weight and bulk. To transport aquatic animals, insert the plastic bag in a second one of equal size, making sure that both are separately sealed when packing is finished. The water in the inner bag should not fill more than one-third of the available volume. The remaining space must be emptied of air and filled with pure oxygen. If gaseous oxygen in not available, it is possible to use commercially available preparations which release oxygen on contact with water.
For more favorable transport conditions, animals should be thermally insulated -- for instance, by being placed in boxes made of expanded polystyrene. Fishes in particular should be transported in the water to which they are accustomed, with the addition of small amounts of disinfectants, anesthetics and antibiotics. The most commonly used anesthetic is MS 222, which should be used in a dilution of 1 :45,000. Methylene blue can be used as a disinfectant when one drop of a 5-percent solution is added per liter of water. A good antibiotic is oxytetracycline, dissolved in water in a ratio of 25-125 mg/I. Fishes should be introduced into treated water only when all the drugs are completely dissolved.
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