Each molecule of water is composed of one atom of oxygen to every two atoms of hydrogen. This is expressed chemically as H2O. Fishes use oxygen, but they cannot use the oxygen that is chemically a part of water. But air, including oxygen, will dissolve in water - just as sugar or salt will - and it is this dissolved oxygen that fishes use.

The major source of usable oxygen in an aquarium is the air above the water. It is therefore at the surface of the water that the major interchange of gases takes place. Carbon dioxide is released by the water at the surface and oxygen is absorbed there. One can drive all the gases out of water simply by boiling it: the warmer the water the smaller the amount of gas it will hold in solution. It is also possible to have an excess of CO2, enough to cause the death of fishes even though there is an ample supply of oxygen present in the water. It is not enough to supply oxygen to the fishes; a means for disposing of the CO2 must also be provided.

In practically all natural bodies of water the surface is proportionately many times greater than the depth. In such bodies of water there is also usually a movement of the water caused by wind, current, temperature changes, and so on. These factors assist in the rapid interchange of gases at the surface so that normally water-dwellers do not suffer from a lack of oxygen or an excess of carbon dioxide. In addition, fishes are seldom as crowded in nature as they are in an aquarium.

Feeding Tropical Fish

Newly bought fishes should not feed for a day after their arrival. They are usually too disturbed to eat, and if the food is not eaten it decomposes and pollutes the water.

After twenty-four hours, feed sparingly once a day. When the fishes have settled down and are eating regularly, start twice-a-day feedings. You should always feed your fish sparingly. You should not over feed the fishes. You should give no more dry food than can be consumed off the surface of the water in one and one-half to two minutes. Always leave the fishes hungry enough to search over the bottom for any food that may have dropped from the top.  The average fish’s stomach is the size of its eye. It can eat at o meal only about as much food as would cover one eye. Very few fishes can eat in the dark.

Very few fishes can eat in the dark. Never feed just before turning the lights off or immediately after turning them on. In the first case, the fishes need time to pick all the food off the bottom; in the latter case, it takes fishes ten or fifteen minutes to adjust to the light after having been in the dark for some time. By the time they have adjusted sufficiently to eat, the food will all have sunk to the bottom.

Signs of overfeeding are recognized as cotton puffs on the bottom and plants, as a gray slime over the bottom, as milky water, and as black gravel. As the particles of food are smaller than the granules of gravel, uneaten food works down into the gravel until it reaches the slate. Foods that are not eaten will lie at the bottom of the aquarium and rots, and as more and more waste food works down, the putrefaction spreads up toward the surface of the gravel.

People are frequently surprised when they stir up the gravel in their tanks and reveal what has been festering below an apparently clean surface. A light, occasional stirring of the gravel will help prevent this situation from developing. Best of all, prevent it by not overfeeding.

How to Prevent Algae from Growing in Your Tropical Aquarium?

It is best to eliminate “green water” before the growth becomes too heavy. Usually this can be done by cutting down the amount of light. This dimming of the light should be done gradually. Cutting off all the light at once can cause the algae to die suddenly, with the resultant of decomposition.

Placing a large quantity of Daphnia (small water crustaceans), which feed on “green water,” in the tank for a few days will also usually clear it up. However, the fishes must be removed or they will eat the Daphnia. They can be replaced to clear up the Daphnia after the latter have done their job.

Fresh-water mussels will also eliminate “green water.” The difficulty is that once they have done the job, they may starve to death and pollute the tank. The quickest method is to dissolve one grain of potassium permanganate by weight to every gallon of aquarium water. This turns the water pink or brown but clears it in a few days. This treatment is also effective for a grayish cloud caused by excess bacterial activity. If the fishes show any distress by hanging at the surface of the water after treatment, change one-third to one-half of the water.

Keeping an aquarium clean will help control algae by depriving them of one of their basic foods - the CO2 caused by decomposition.

Changing all or part of the water is worse than useless. Fresh water acts as a stimulant and actually increases the growth of algae.

The other algae are thread algae, blanket algae, and filament algae which will all yield to decreased light. Siphoning can remove much of the blanket algae. Plecostomus catfish and snails will eat the filamentous types. A fork can be used to entangle and uproot thread algae, while a stiff brush will remove it from rocks and ornaments.

What is the best way to light an aquarium?

The aquarium should be lighted from the front and the top. The rays of the light should be directed down and back toward the rear, bottom. They should be directed away from the viewer’s eyes, striking the fishes directly to reveal their beauty. Light coming from the rear tends to silhouette the fish and to conceal refractive colors.

As a general rule, eight to ten hours of light a day, utilizing the wattages given, will result in satisfactory plant growth. Larger wattages may be used for lesser periods of time, and smaller wattages for greater. That there is a point of diminishing returns is obvious. Too low a wattage will not penetrate a depth of water; too high a wattage may overheat the upper layer of the water. Observation over a period of time will determine the most satisfactory wattage to use and the proper period of time to keep the lights on.

The most satisfactory arrangement is one that keeps the plants healthy and the algae growth down to a minimum. Should the plants start to deteriorate, usually more light is required; that is, higher wattages or a longer period of illumination.

Excessive growth of algae usually indicates too much light and, possibly, an excess of decomposing organic matter. The remedy, usually, is to decrease the amount of illumination and to siphon off all excess food and foreign matter. A certain amount of algae is bound to form even under ideal conditions. But you can keep this minimal growth in check by scraping and by using scavengers. You should be most concerned with the wild, seemingly uncontrollable growth that coats the rocks and plants and turns the water green.

Certain colors, although pretty to see, actually inhibit the growth of plants. The warmer tones at the red end of the spectrum are the most satisfactory for plant stimulation. Blue colors are the least helpful. The most practical are the uncoated clear glass bulbs which have a long filament. Although there are a number of inexpensive bulbs on the market which have short filaments, actual tests have proven them to be less effective than the long in stimulating plant growth. Any coating on a bulb must of necessity diminish the amount of light reaching the plants and thus decrease the effectiveness of the bulb.

Introducing Fish into the Tropical Aquarium

Many people receive fishes shipped from out-of-town sources. Often prompt and proper action must be taken upon their arrival to insure their continued life.

Examine the carton carefully before opening it. If it is wet or damaged, mark the fact on the receipt before signing it. Make the carrier wait and watch while you open the shipment. Check the water temperature immediately. Do not remove any fishes which appear to be dead, unless they are obviously decayed or physically damaged. Many tropical fish can be revived.

If the water is below 70° F., it is important to warm it to a higher temperature. Do not remove the fishes and put them into other warmer water. Instead, add warm water to the original water. Stir as you add the warm water to prevent hot water from touching the fishes. Warming the water slowly is dangerous. The fishes may die before the water gets warm enough to help them.

Once a desired temperature has been reached, change part of the water for fresh water. If the original water was foul, continue making partial changes at intervals until the water is clear. The water which is dipped out is thrown away. This process over a period of hours will give the fishes a chance to adjust to the different composition of your water.

Fishes bought from local source are usually brought home in a small container. These containers should be allowed to float unopened in the aquarium for fifteen minutes. This allows the water in the container to equal the temperature of the tank water. Remove the cover carefully. The fishes are likely to jump as soon as they see the light. Partially submerge the container slowly so that some water from the tank gradually runs into it. Pour out part of the water and repeat. Do this several times before completely submerging the container and letting the fishes swim out.

When transferring fishes from one tank to another, the same procedure is followed. Dip some of the fishes’ own water out in a container and place the fishes in that for transferring. It is unnecessary to float the container first,

Many aquarists maintain newly acquired fishes in separate tanks for ten days or two weeks. This helps to reveal any latent disease before it might be transmitted to the other fishes. During this time strict isolation is practiced. Utensils (net, dip tube, etc.) are disinfected, water drips are avoided, and even hands are scrubbed and rinsed thoroughly before going from one tank to the other.

A fairly good isolation ward for two or three small fishes is a squat one-gallon jar floating in the aquarium. By experimenting with the amount of water in the jar you can determine the proper amount to keep it upright and buoyant. This type of jar can be used for breeding also. A breeding trap, with its perforations which permit the circulation of water, is of course valueless for isolation.

Tropical Aquarium Aeration and Filtration

Water is the fishes’ atmosphere. It is the medium in which they normally exist and through which they travel, and from which they extract the oxygen so necessary to existence. Just as our air must be pure and contain sufficient oxygen, with no excessive amounts of harmful or irritating gases present, so must the fishes’ water be clean and well oxygenated.

Provision must be made to prevent the accumulation of harmful materials in the water; whether gaseous, solid, or liquid; whether in solution or suspension. The fishes’ water, just as the air we breathe, always contains a certain amount of harmful material; that is, material which would poison the fish if allowed to accumulate above a certain minimal amount.

The atmosphere over every large city contains tons of waste matter such as factory gases and products of combustion. When weather and geographic conditions prevent their dispersal, they can accumulate in such quantity as to inhibit human life. It is this sort of situation which is described as “smog.” The same sort of thing, on a lesser scale, can occur in our aquaria unless we guard against it.

The problem is twofold: to insure a proper supply of oxygen for the fishes to use, and to dispose of the products of respiration, metabolism and decomposition.

Oxygen is the fuel that stokes the furnace of life. This is true of fishes as well as of higher forms of life. The majority of fishes breathe by taking water in through the mouth. The mouth is then closed tightly and the water is forced outward over the gills and through openings at the back of the head. Each of the openings is covered by a flap - the operculum - often incorrectly called the “gills.” The gills are located under the opercula. They are the red branching members seen when the gill flap is lifted.

A few varieties of fishes, such as the Bettas and certain Catfishes, have specialized auxiliary breathing organs which enable them to extract oxygen directly from the atmosphere. However, such fishes are in the minority. It is the gills of the vast majority of fishes that are analogous to our lungs. As the water passes over the blood-rich gill surface, the dissolved oxygen is extracted for the fishes’ use, and waste carbon dioxide is given off.

A fishes’ nostrils are not used for breathing. The nostrils do not connect with the mouth and are used solely as organs of smell. There are a very few exceptions to this, but they are not included among the fishes kept in home aquaria.

What is a cover glass and how does it fit?

A cover glass is an aquarium cover. It is best made of light plate glass so as to be more break-resistant. When used with a reflector, the glass should start from just behind the reflector and cover the balance of the tank. Under no circumstance should the cover glass be extended under the incandescent reflector. The heat of the bulbs is likely to crack the glass. Also, the glass coming between the light and the tank may filter out a good deal of the light and retard plant growth. With a hood, no cover glass is necessary.

The rear corners of the cover glass may be cut out for a heater and/or filter. There are clips and handles available which can be fastened in place to suspend the cover glass inside and just below the rim, rather than having it rest on the rim of the tank. These are helpful because they prevent moisture from gathering between the glass and tank rim and corroding it.

When neither reflector nor hood is used, a cover glass should protect the whole aquarium. The functions of a cover glass are many. It helps regulate the temperature, prevents fishes from jumping out, reduces evaporation, keeps out dust and dirt, and also keeps out inquisitive fingers and paws !

For a tank kept in a sunny or extremely light location, the cover may be of translucent glass to cut down the glare.

For proper aquarium heating, you need a source of heat that can be regulated. The heat given off by the reflector is incidental. Most people turn their reflectors on in the evening when the house is at its warmest and turn it off when they go to bed. Should they be dependent solely on the reflector for heat regulation this would result in the tank temperature being at its peak during the evening and plunging rapidly down during the night, when the light and usually the central heating system are both turned off. This could be disastrous. Unless you are prepared to keep a close watch on your tank thermometer, turning on the light as the temperature drops and turning it off when the heat rises, you cannot depend on the reflector. Actually, you would be turning yourself into a thermostat. It is much more practical to buy one.

Breeding Traps for Live Bearing Fish

Breeding traps are plastic containers. There are three types: the rod trap, the “V” bottom, and the combination nursery and breeding trap. They are all designed to hang inside an aquarium and receive heat from it. They are also perforated to allow water circulation. Very little actual circulation takes place, however, unless it is helped along by dipping breeding trap. The excess will, of course, run out through the perforations. Usually a breeding trap is set in the rear of the aquarium where its inhabitant will not be disturbed.

The rod trap is a square box about 8 inches long by 4 inches wide by 4 inches high. The bottom consists of glass or plastic rods set a little apart from each other. The pregnant female is confined in this type trap with a few sprays of plants for hiding herself. This is important, because in a bare trap there is more of a tendency for her to thrash around. When the young are born, they drop through the bottom and are protected from the possible cannibalism of their mother. Of course there should be no fishes in the aquarium into which the babies drop. The rod trap that is longer (up to 18 inches), is also used for breeding certain egg-laying fishes, such as Zebras (Brachydanio rerio) and White Clouds (Tanichthys albonubes), which lay non-adhesive eggs.

The “V” bottom trap is shaped so that the bottom comes to a long V. The sides are perforated. Babies, when born, drop out through the slit. This type is also provided with a plastic rod or strip which can be used to close the bottom and prevent the babies escaping. This is used when there are fishes in the larger aquarium which might at the babies. Of course they are still in danger of being eaten by the mother, but putting some hiding plants in the trap will help save at least some of them.

Do not overdo the hiding plants, however; leave room for the mother.

The combination breeding and nursery trap is a square box with a “V” insert in it. When born the babies drop through the opening in the bottom of the breeding trap and are confined in the lower portion of the trap. After delivery, the mother and the insert are removed, giving the young ones a nursery to swim around in. As might be expected, this type is somewhat more expensive.

Since all of these breeding traps are comparatively small, it is inadvisable to keep large females in them. They will suffer from the confinement. And of course never keep two females in the one trap. Cover breeding traps, because even baby fishes can jump.

A trap is not so satisfactory a method of raising babies as a separate nursery tank is. It is, however, of great value to the person who cannot keep more than one tank and still wants the thrill of breeding his own fishes. A breeding trap may also be used in conjunction with a baby tank. Obviously you cannot keep an adult gravid female with the babies while she is awaiting delivery. A breeding trap is placed in the baby tank and her babies join the others as they are born.

Whether in a trap or a tank, babies must be fed. To accomplish this, use special baby foods. Feed small amounts, but feed frequently. Do not give the little stomachs a chance to get empty. Do not make the meals too big, as the excess will spoil before the babies have had time to eat it.

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