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Choosing an Aquarium

Tropical Aquarium

Choosing an aquarium is a vital choice for the health and wellbeing of your tropical fish.

So why is your choice of aquarium so important? It is important because the surface area of your aquarium has a direct impact on the number of fishes that your aquarium can sustain in good health.

Tropical fish are very similar to humans in that without sufficient oxygen or with too much carbon dioxide your fish will become ill and, ultimately will die.

Respiration of Tropical Fish

Tropical fish have gills rather than lungs. The gills are able to extract the oxygen from water and, in the same way that humans use their lungs to obtain oxygen for their bodies. That oxygen migrates into the fish’s bloodstream to enable the organs of the body to function.

Fish exhale carbon dioxide in the same way that humans exhale carbon dioxide. The exhaled carbon dioxide is dissolved into the water. If there was no movement in the water then the carbon dioxide would build up and the fish would suffocate.

The Water Surface

The only way that carbon dioxide can be released from the water is by releasing it at the surface of the aquarium. This is where all of the magic happens. Carbon dioxide is released and replaced with oxygen.

This has been tested by placing fish in an aquarium where the water surface has been covered by a paper of plastic film. This film prevents the escape of carbon dioxide and also prevents fresh oxygen being dissolved in the water from the atmosphere.

Gradually, the oxygen in the water becomes depleted by the respiration of the fishes whilst, at the same time, the amount of carbon dioxide increases. As the fishes start to find respiration difficult they will move towards the surface of the water in order to try to find fresh oxygen.

The surface of the water is where all of the magic happens that enables your tropical fish to thrive. In fact, the surface area of your aquarium is the first key factor in determining how many fishes your aquarium can sustain in a healthy manner.

The Proportions of your Aquarium

Aquariums come in all shapes and sizes. Starting, I suppose, with the humble goldfish bowl, even this has a critical impact on how many fishes can live healthily in the bowl. If the bowl is filled with water to within one inch of the top of the bowl then it can sustain fewer fishes than if it were only half-filled. This is because there is much less water surface near the top of the bowl than there is in the middle. With a smaller surface area, less carbon dioxide can be released and less oxygen can be absorbed into the water.

If you choose a tall, narrow aquarium then this will sustain no more fishes than if that aquarium was only half the height simply because the surface area fundamentally affects how much oxygen can be absorbed into the water.

A narrow aquarium will also affect the size to which larger species of fishes can grow. For smaller species such as the Tetras, a narrow tank is unlikely to affect their ultimate size whereas for larger species such as the Cichlids or a Discus then a narrow tank would make it difficult for such fish to turn around if they grew to their full size (or were introduced full-size to the tank) so their growth might be limited by the restrictions of their environment.

Adding Aeration to your Aquarium

Adding aeration to your aquarium, at a basic level, involves buying an air pump, some plastic tubing and an air block.

The pump sits outside the aquarium. The tubing is attached to the pump at one end and to the porous block at the other end. The porous block is placed into the tank, usually at the rear corner so that when the pump is switched on it pumps air through the tubing and the air block and fine bubble of air come out of the block and rise to the surface of the tank.

This flow of air causes the circulation of the water. At the same time that the air floats to the surface, water is moved upwards alongside the water. This also moves any dissolved carbon dioxide to the surface where it can be exchanged for fresh oxygen.

The surface of the water is now being disturbed by the rising bubbles of air so the surface begins to ripple from that corner across the entire surface of the tank which further increases the amount of oxygen absorbed by the water.

Thus, by adding aeration to the tank the amount of dissolved carbon dioxide is reduced and your fishes are much happier.

Adding Plants to your Aquarium

You can further enhance the health of your aquarium by adding plants. Some plants have particularly efficient oxygenating properties. They absorb carbon dioxide and release oxygen into the water. In addition, they provide safe places for smaller fishes to conceal themselves from larger fishes.

Plants placed strategically within the aquarium can add interest to the observer because, at any one time, whilst some fishes will be visible to the observer, others will be swimming or resting behind plants. Over time, fish will emerge for a while and disappear from view so not everything will be on view at the one time. The observer can spend many hours watching the peaceful world of the aquarium, as the fishes go about their business, sometimes individually, sometimes as small shoals.

Adding a Filtering System to your Aquarium

In the wild, water flows downstream so it is constantly on the move. This process helps in removing unwanted material.

In your aquarium, the water isn’t going anywhere so you need to add a water-filtering system to eliminate toxins from the water. There is a huge range of water-filtering systems on the market, some are fitted inside the tank whilst others are external.

In essence, the system pushes the water through one or more filters which trap any toxins in the water and the cleaned water is then returned to the tank. Periodically you will need to replace or clean the filters to ensure that the water is kept in optimum condition for your fishes.

Lighting your Aquarium

Always remember that your fishes are living creatures so, like all creatures, have a circadian rhythm of night and day. With your aquarium, so far as is practical, seek to give your fishes a balance of night and day in their artificial world.

Other than switching on the light in the morning and switching it off again at night you could use a timer to do the job for you.

Plants can offer shade from direct light, just as they do in nature.

Heating your Aquarium

Depending on where you live you may need to heat the water in your aquarium to ensure that the water temperature is correct for your fishes.

Typically, an ideal temperature of around 75 degrees Fahrenheit should be your target temperature.

In choosing heaters it is best to have relatively low-powered heaters that will heat the water very slowly. This is because the heaters are controlled by thermostats and thermostats can fail. If a thermostat fails and you have powerful heaters then your fish will cook. If, on the other hand, the heaters are sufficient to increase the temperature very slowly then you will have the chance to replace a faulty thermostat before your fishes are cooked alive.

As a general rule, 2 watts will maintain one-gallon of water at a temperature five degrees Fahrenheit above the surrounding air so if your room temperature is around seventy-degrees and you have a twenty-gallon tank then 40 watts will maintain the tank at seventy-five-degrees.

Get the largest Aquarium that you can accommodate

Whilst you can quite easily provide a healthy environment for a few small fishes in a five-gallon tank it is recommended that you get the largest aquarium that you can afford to provide a much more interesting environment for many more fishes of different species.

Your fishes will spend their lives in your aquarium so give them the best quality of life that you can offer them. Whilst you are unlikely to be able to provide them with their natural environment you can certainly come close by making the effort needed and by choosing the most appropriate aquarium.

Choosing and aquarium – Video

How to know that your aquarium is healthy

There is no single way that you can say that you know that your aquarium is providing the ideal environment for your fishes but, as a rule-of-thumb, if your fishes use the entire tank, from top to bottom and front to back than this is generally a good indication that all is well.

If your fishes tend to hover around the top of the tank then either there are too many fishes or too little oxygen in the tank (or both).

Rather than filling your tank with fish just as soon as you can, introduce them gradually and give them time to settle in before you add more fishes.

Featured image courtesy of: Aleš Tošovský

Mike Wheeler

I started keeping freshwater tropical fish in 1972 and it has been something of a passion ever since. In this website, my aim is to build up an everyman's guide to help the everyday aquarist get the best from this inspiring and entertaining hobby.

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