Aquarium Basics

aquarium basics, introduction
With the proper planning and preparation, keeping an aquarium can be a rewarding experience. See more aquarium pictures.
© Perfecto Manufacturing

Keeping an aquarium can provide immeasurable rewards and satisfaction. It does, however, require some work as well, and before you venture into the hobby, you'll need some fundamental information.

Aquarium Image Gallery


The best way to begin is with a basic understanding of what happens in a successful aquarium. You'll also need to know how to select a good aquarium store, one that can provide you with reliable equipment, service, and advice.

Finally, you'll need to take the first step in planning your aquarium: selecting a tank and a suitable location for it.

Let's begin by exploring the closed aquatic environment on the next page.

To learn more about freshwater aquariums, see:


The Closed Aquatic Environment

aquarium basics, diagram
Natural aquatic ecosystems are much more complicated than the aquatic environment of an aquarium.
©2007 Publications International, Ltd.

It's actually amazing that fish can survive in an aquarium at all. Compared with their natural habitats -- from jungle streams to vast lakes -- even a relatively large aquarium is tiny.

An aquarium also has several built-in limitations that work against the health of its occupants. No matter how extravagant and no matter how carefully planned, any aquarium is an artificial environment.


Natural aquatic ecosystems are much more complicated than the aquatic environment of an aquarium. The biological processes in a body of water have been finely tuned over millennia to become a complex, living system.

This system includes weather patterns, geological and chemical processes, and countless interrelationships among plants, animals, and microorganisms. The lifeforms found in these systems have adapted to very specific conditions, and their ability to survive depends on their environment.

A closed system like an aquarium is a completely different thing. By definition, a closed system means that the environment consists solely of the tank and its contents. The natural processes that, in the wild, would provide food, protection, and a clean, uncontaminated environment for the fish are not a part of the aquarium.

As a fishkeeper, your primary responsibility is to see that these things are taken care of in the confines of your aquarium.

Providing nourishment and a safe and comfortable habitat are essential. Maintaining the water quality, however, is something a bit less obvious to most new aquarists.

Water quality refers to the amount of debris, pollutants, and other undesirable substances that appear in the water either naturally or through contamination, and more aquariums fail due to poor water quality than probably anything else.

Why is water quality so important? Approximately 80 to 90 percent of all fish diseases are due to physical stress. The most common source of stress is from living in polluted water.

This stress, if persistent and unrelieved, causes the immune system of a fish to become less and less able to fight infection from disease-causing organisms that are always present in the water. Some species of fish suffer from this problem more quickly than others, but all fish eventually become sick and die when kept in poor-quality water.

Beginning aquarists may have a difficult time keeping their aquariums healthy not because they lack skill or motivation but because they lack knowledge. Keeping water clean is actually not difficult at all; it requires only a little understanding, a little effort, and the right equipment.

Go to the next section to find out more about the importance of aquarium water quality.

To learn more about freshwater aquariums, see:


Aquarium Water Quality

aquarium basics, water quality
The presence of plant life and fish overcrowding are two big factors in aquarium water quality.
©2007 Publications International, Ltd.

Aquarium water quality deteriorates for several reasons. As a part of their metabolism, fish produce various waste products that accumulate in the water, and other organic matter such as uneaten food decays into substances that can contaminate the water.

Over time, these pollutants build up in an aquarium to a level that is dangerous to the occupants. In their native environment, fish are protected from this problem by a natural system. The water in a river or lake is continually replenished with fresh rainwater, and different chemical and biological processes remove organic pollutants from the water.


To keep a healthy aquarium, you simply need to understand this natural system and duplicate its effects for your fish.

Prior to the advent of filtration, hobbyists depended on their ability to maintain a balance in the tank. The number and size of fish, the abundance of plants, and the ability of snails and other scavengers to consume excess food and other materials in the tank were all taken into consideration.

It was, however, a balancing act that only the most skilled aquarists could maintain over time. The number of fish that could be kept in these balanced or natural aquariums was rather small. And yet, when measured against the natural environment of the fish, even these aquariums were rather overcrowded.

Today, new hobbyists often believe that aquarium technology, particularly the filtration system, eliminates the work and the problems of keeping fish. Up to a point, this is true.

Certainly in comparison to keeping fish in a bowl, where all of the water must be changed at least once a week, an aquarium with a filter is more convenient and easier to maintain. Still, filtration systems have limitations.

No matter how sophisticated, a filter can only slow down the rate at which the water in an aquarium becomes polluted. No filter system can actually stop water quality from deteriorating. Filtration is important to maintaining good water quality for the fish, and filters do make it possible to keep more fish in an aquarium.

Success with fishkeeping, however, requires more than a good filter. The true value of filtration is that it helps you maintain good water quality more consistently, but only if some easy-to-follow principles of aquarium care are followed.

The real key to success is found in three basic rules, each formulated to create a stable environment for the fish. Rule one is to not overstock the tank with fish. The more fish there are in an aquarium, the faster the water quality goes down. As noted earlier, the filter only slows this process.

The second rule is to not overfeed the fish. The accumulation of uneaten food in the tank will quickly contaminate the water. Rule three is to do frequent partial water changes. This removes pollutants and adds fresh, clean water to the aquarium, helping to maintain a healthy habitat.

If you understand these three rules and the reasoning behind them, you're well on your way to becoming a successful aquarist.

What remains is to learn about the equipment you'll be using -- what you need and why you need it -- and then to learn a little about the fish that you'll be setting up house for. Let's continue with learning where to shop for your aquarium on the next page.

To learn more about freshwater aquariums, see:


Where to Shop for Aquariums

aquarium basics, pet store
Finding a good pet store is essential before launching into your new hobby.
©2007 Publications International, Ltd.

New hobbyists seldom realize how valuable a good pet store is to their success in fishkeeping. Value, in this case, has nothing to do with the lowest prices or shortest driving distance.

When determining where to shop for aquariums, what you want is a store that can offer good advice, provide solutions to problems, recommend products that will best serve your needs, and handle warranties or repairs for equipment.


If you live in an urban area, you probably have dozens of pet and aquarium stores to choose from. The smaller the city or the more rural your area is, the fewer shops there will be.

One of your first goals is to visit as many aquarium dealers as are convenient before you purchase anything. As you visit each store, there are certain things to look for. The shop should have a clean appearance. The floors should be swept and the carpets vacuumed.

Shelves should be stocked with a variety of merchandise. Dust, particularly on containers of food, means a low turnover of goods, increasing the likelihood of old or outdated products.

The tanks themselves should look well kept. The water should be clear and the front glass clean -- no water spots on the outside or algae on the inside. The tanks should be clearly labeled with the names and prices of the fish contained within them.

The fish should be healthy and active; that is, individual fish should display color and behavior that is typical of the species. In a large store with many tanks, the occasional dead fish in a tank can happen. However, if many of the tanks contain dead fish, or if the employees seem uninterested when a dead fish is pointed out to them, you'll want to take your business elsewhere.

If the fish aren't healthy when you buy them, they are unlikely to become healthy in your own aquarium, and they could be carrying disease that will affect your other fish.

Note whether the dealer has a good selection of nice-looking live plants. Even if you end up using artificial plants, a store that stocks specialty items like good-quality live plants is much more likely to serve the needs of hobbyists at all levels.

Also look for a display of aquarium books. A large and varied number of titles indicates a dealer who knows how important reading about the hobby is for aquarists -- particularly beginners.

The quality of the sales staff is also important. They should be knowledgeable about the hobby in general and interested in your questions. They don't have to know the answer to every question, but they should be willing to find out what the answers are.

Do not simply patronize the shop with the lowest prices. As often as not, the shop with the lowest prices has the least knowledgeable staff, the poorest selection of merchandise, and the least healthy fish. It is always better to pay a little more to a reliable dealer who will support you and help you grow in the hobby.

After you've purchased your aquarium, you'll want to put it in the most optimal spot in your home. Learn about choosing an aquarium location on the next page.

To learn more about freshwater aquariums, see:


Choosing an Aquarium Location

aquarium basics, location
Finding the proper location for your aquarium is key to your own enjoyment as well as to the health of your fish.
© Perfecto Manufacturing

There are three basic factors to consider before actually purchasing an aquarium. You want to decide where the tank should go, what kind of fish you want to keep in it, and how much money you feel comfortable spending. You should really make these decisions before bringing home a tank. Aquariums last for many years, and if you make the wrong choice, you may have to live with it for a long time.

The first thing on the list is choosing an aquarium location. It is important that you be able to view the aquarium easily from a favorite chair. Keeping the tank in an area where you spend a lot of your time will enhance your enjoyment of your fish and your interest in fishkeeping.


Sitting comfortably and watching the fish lets you appreciate them, and it also provides an opportunity to note if they are behaving normally. Experienced aquarists can catch problems early by simply noting changes in the behavior of their fish.

The tank also has to be in a place that offers ready access. Although an aquarium doesn't require much maintenance, it does need some. If it is difficult to work around the tank because of a lack of space, you will be much more likely to put the work off and let the water quality deteriorate, and as a result, keeping your aquarium healthy will become much more of a chore.

The location of the tank should also be determined by the room's light, temperature, and traffic. One of your goals is to provide the fish with a stable, secure environment. This is much easier to do if you can control these factors.

Sunlight coming through a window or door can overheat the tank, particularly in summer, raising the water to lethal temperatures. Excess light can also cause significant algae growth in an aquarium. The combination of warm water, sunlight, and nutrients in the water encourages unwanted algae to multiply and cover every surface in the aquarium.

Nearby windows and doors can subject the tank to drafts of cold or hot air, making it harder to maintain a consistent water temperature. Rapid changes in temperature create enough stress to cause some fish to become sick. For this reason, the tank should also be kept away from radiators, vents, and other sources of hot or cold air.

Heavy traffic around the aquarium can be very disturbing to many fish. If people are continually walking by the tank or if nearby shelves or furniture receive frequent use, the activity can stress the fish and make it more difficult for them to thrive.

See the next section to learn about choosing an aquarium display.

To learn more about freshwater aquariums, see:


Choosing an Aquarium Display

aquarium basics, stands
Smaller tanks such as this one can sit safely on a table or another piece of furniture.
© Perfecto Manufacturing

In addition to picking the location, you must take time when choosing an aquarium display. The tank must sit on a sturdy support. A table or other piece of furniture is seldom suitable except for the smallest of tanks.

The weight of a typical aquarium is roughly 10 pounds per gallon, so a 10-gallon tank will weight about 100 pounds and a 30-gallon tank will weigh about 300 pounds. Most furniture is not designed to support that kind of weight. The furniture would also suffer from the effects of spilled and splashed water, which is a virtual certainty no matter how careful you are.


For these reasons, the best way to support an aquarium is with a stand designed specifically for this purpose. These are usually made from wood or wrought iron, sometimes with a second shelf for another aquarium or for supplies and equipment.

Even better are stands with doors to hide air pumps, filters, food, and other items. If you are willing to spend the money, custom-crafted aquarium furniture can make the aquarium fit perfectly into the decor of any room.

The floor itself must be level and capable of withstanding the total weight of the aquarium and support. The main reason for needing a level floor is to avoid uneven stresses on the tank that might cause a leak. It also looks better if the water line is even at the top of the tank. With most tanks, weight will not be a problem.

However, for very large aquariums, 100 gallons or more, some floors may have to be reinforced. One problem with most stands is that all of the weight is actually transmitted to the floor at only four points, where the legs are. It may help to distribute the weight more evenly by placing lengths of wood under the legs.

Go to the next page to find out about choosing the right size aquarium for your space.

To learn more about freshwater aquariums, see:


Choosing Aquarium Dimensions

aquarium basics, dimensions
The numbers and sizes of fish that can be kept are affected by both the tank size and tank dimensions.
© Jeffrey Beall

Your next concern is choosing aquarium dimensions, which includes both the size and shape of the aquarium.

Ideally, you want to purchase the largest tank possible -- one that you can afford and that will fit into the chosen space. A larger aquarium will hold more fish, of course, but greater size will also provide a more stable aquatic environment.


As the volume of water increases, it can be easier to maintain consistent water temperatures and good water quality. This is not to imply, however, that a modest-size tank will have problems. With a little care and attention, any tank of 10 gallons or more can be a healthy home for fish.

The cost of an aquarium rises moderately with its size until you pass capacities of about 55 gallons, at which point prices rise much faster. The amount of glass needed for very large tanks and the increased thickness required as the tanks become deeper contribute to these price increases.

The numbers and sizes of fish that can be kept are affected by both the tank size and the tank dimensions. For this reason, it may help to know what kinds of fish you want to keep when shopping for an aquarium.

If you don't want to plan that far in advance, just be aware that you may have to avoid certain types of fish if your aquarium is not suitable for them. Don't worry, though; no matter what kind of tank you buy, you'll be able to choose from a great variety of potential residents.

You will discover that aquariums of similar or identical capacities can have very different dimensions. While the amount of water that an aquarium holds is important, many new hobbyists do not realize that the dimensions of a tank can be important, too.

The length and width of the tank determine the surface area of the water, and surface area directly affects the number and size of fish that can be kept in the aquarium. The significance of surface area may not be clear until you understand a little more about the biology of an aquatic environment.

One of the most important rules of successful fishkeeping is to not overstock your tank. Overcrowding can make it all but impossible to keep fish alive and healthy.

Increasing the filter size and the amount of maintenance can partially compensate for too many fish, but in the long run nature takes it course and fish will sicken and die until the aquarium is no longer overcrowded.

Exactly what constitutes overcrowding, however, is hard to say. Looking at the tanks in stores is no help because these aquariums are vastly overstocked. The short amount of time the fish are in these tanks, combined with extensive filtration and frequent maintenance, allows retailers to maintain heavy tank populations.

Learn more about choosing an aquarium size in our final section.

To learn more about freshwater aquariums, see:


Choosing an Aquarium Size

aquarium basics, size
Hexagonal aquariums such as this one can make very attractive displays.
©2007 Publications International, Ltd.

For many years, aquarists have used guidelines that relate the size of the fish to the volume of the tank. The most common guide when choosing an aquarium size is one inch of fish per gallon of water. This refers to adult fish and does not include the tail.

Although not a bad rule of thumb, this guideline has two major shortcomings. First of all, a fish's length does not by itself indicate the total impact the fish will have on a closed aquatic system.


While some fish are slim, others have much fuller bodies. As fish grow, their weight or mass may increase much faster than their length. The end result is that an aquarium may meet the guidelines of an inch of fish for every gallon of water but still be overstocked or understocked.

The second problem with this guideline is that it doesn't account for surface area, which is a real limiting factor. Fish require oxygen to live. They remove dissolved oxygen from the water and release carbon dioxide into the water, so the dissolved oxygen content of a tank is one of the things that determines a safe stocking level.

Oxygen enters the water from the atmosphere at the surface, and carbon dioxide is released into the atmosphere at the surface. The greater the surface area, the greater the exchange of oxygen and carbon dioxide and the more fish the tank can support.

To take surface area into account, a good guideline for stocking an aquarium is one inch of adult fish (not including the tail) for every 24 square inches of surface area. This also does not account for the

difference between slim and broad fish, but this rule of thumb at least provides a greater margin of safety.

This guideline, by the way, is for tropical aquarium fish. Cold-water fish, such as goldfish, need 30 square inches of surface area per inch, which takes into account their much greater body mass per inch and greater oxygen requirements.

What all of this means is that when choosing an aquarium, it is best to try to select the one that has the greatest surface area for a given volume. If you choose a tank shape that offers less surface area, take that into consideration when stocking it.

Aquariums of the same capacity but different surface areas come in three basic types: regular tanks, show tanks, and long tanks. Show tanks tend to be taller than regular tanks, thus providing a larger front glass area to view the fish but a smaller surface area. They are narrower front to back than normal tanks.

Long tanks have a greater length than regular tanks, making for a very attractive display tank and increasing the surface area. Show tanks are particularly well-suited for deep-bodied fish, such as angelfish, whereas long tanks are good choices for territorial species or for fast-swimming, schooling fish.

A different tank shape is the hexagon aquarium, with six sides. These can make very attractive displays, but keep in mind that the surface area of this type of tank is less than that for a normal tank of the same volume.

Round or bubble tanks are even worse in this respect because the maximum amount of surface area is available only when the tank is half full. As the water level goes higher than this, the surface area decreases. This is the same problem that plagues goldfish bowls.

Worst of all are very tall, thin aquariums, which have the surface area of a much smaller aquarium.

Recently mini aquariums ranging from two to six gallons have become very popular. While they are attractive and inexpensive, these tanks can be very difficult to maintain. They hold limited amounts of water, they have only a minimal surface area, and they often come with inefficient filter systems.

Even experienced fishkeepers have a very difficult time maintaining healthy fish in tanks of this size.

To learn more about freshwater aquariums, see: