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.

Tropical Fish Tanks - What is an Aquarium Heater?

A heater is the apparatus which provides the actual heat as opposed to the thermostat, which is the automatic switch for controlling heat. The majority of heaters made today are fabricated of nichrome resistance wire, which is wound around a ceramic core. Some are of nichrome which is wound on an asbestos backing, and a few have the resistance element imbedded in the ceramic. The tube may or may not be filled with sand.

Heaters are divided into two groups: those which are attached directly to a thermostat, either in the same tube or an adjoining one and those called combination heating unit, thermostatic control, condenser and pilot light. For convenience these items may be housed in the same tube with an attached hanger, or they may be located in two different tubes with a clip joining them and a hanger.

At the present time there is only one combination heater and thermostat that can be completely submerged in water. Most of them are designed to hang vertically on the aquarium, partly in the water. I specify “in the water” because I have found that a good many people, unless told otherwise, hang such heaters on the outside of the tank.

The water level should be one to two inches below the lip of the tube (or tubes) to prevent water from entering I lie heater. Always read and follow the manufacturer’s instructions carefully.

The cover glass (or hood), if used, should be cut away above the heater and/or thermostat to prevent condensed water from dripping into it.

The combination unit may have a knob on the top to adjust the temperature regulator. This is called an “outside-control.” An “inside-control” unit has the mechanism attached to the rubber cork stopper. Removal of the stopper lifts the unit, allowing the adjusting screw to be reached. It is advisable to unplug the unit before is removed for adjustment.

A word of warning: never put a hot heater into the water; it will crack. Always disconnect a heater before removing it from the water.

The heaters which are made independent of a thermostat may be sealed for submersion or may be hung on the side of the tank. These and the other types may be sand-filled.

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.

Tropical Aquarium - Should incandescent or fluorescent light be used?

Some reflectors are fitted with sockets for a fluorescent tube instead of incandescent bulbs. There is a good deal of controversy concerning the relative merits of the two systems. Experiments conducted by Dr. C. W. Coates at the New York Aquarium indicated that a combination of both incandescent and fluorescent lighting gives the most satisfactory results. His experiments also showed that light, in order to be satisfactory, must be directed from above. Light from the side has a greatly decreased value.

It is impractical for the average hobbyist with a small or medium aquarium to use both types of light, however. Properly used, either will give a satisfactory growth to the average aquarium plant, although it may not necessarily give maximum growth.

The initial outlay for a fluorescent fixture is slightly higher than that for an incandescent. This is offset by the fact that a fluorescent bulb consumes much less current. Also, the higher cost of a replacement tube for a fluorescent is balanced by its longer life. In addition, fluorescent fixtures give a stronger, more even light, and they do not heat up the aquarium. This is particularly important during the summer, when preventing any increase in the already high water temperature and yet supplying enough light for the plants can be a problem. When using a fluorescent, the red end of the spectrum should be favored for color because it is the most beneficial. White, cold white, and daylight bulbs are not so satisfactory as warm tints, warm tones, or deluxe warm whites.

As with an incandescent, the time for the required for the fluorescent to obtain results is extremely variable. In general it should burn two to three times as long as an incandescent reflector under comparable circumstances.

For tanks of 20 to 30 gallons in capacity, the standard reflector holds a 20-watt bulb. It is frequently necessary to burn a bulb of this size twenty-four hours a day in order to achieve satisfactory plant growth. For smaller tanks, sixteen to twenty hours of light a day is usually necessary. If it is inconvenient to turn the light on and off at the time necessary to provide the proper illumination, it is perfectly satisfactory to burn the light twelve hours one day and twenty four hours on alternate days.

One of the most satisfactory tanks I had experience with was a 27-gallon aquarium owned by a businessman. It measured 36 inches long by 12 inches wide by 14 inches high, and was equipped with a 20-watt warm-white fluorescent fixture which burned continually. The plant and fish growth in that tank was phenomenal. Ambulia, Amazon Sword Plants, Hygrophila, and Cryptocoryne of different species grew in profusion. Magnificent fish luxuriated among the dense growth. No attention was given to the tank other than feeding and replacing water lost through evaporation. Every month a pet shop owner was called in to siphon the bottom clean, and to remove a pailful of excess plant growth.

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.

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