Nature has created over 30,000 species of fish, and with the sophisticated aquarium systems now available, literally hundreds of them can be successfully kept in the home. The art of fish-keeping can be as simple or as complicated as you care to make it – from a single goldfish in a plastic bowl, to a breathtaking display of tropical beauties in a massive glass tank. But, it’s important to consider how much time and effort you wish to put into this new hobby. Your first consideration as a potential fish keeper will be to decide on which type of fish you intend to have in your home.

You can choose from four different groups: coldwater freshwater fish, tropical freshwater fish, coldwater marine fish and tropical marine fish. While the first of these types can be successfully kept with very basic equipment, the last will inevitably be the costliest and most demanding of your time and attention. One thing is for certain, whichever group of fish you ultimately decide on, you’ll need some kind of tank in which to house them. Let’s take a look at the various types of tanks currently on the market.

Basic Fish Bowl

Many people keep coldwater freshwater fish (usually goldfish) successfully in plastic or glass bowls. Although in many ways this is the simplest approach to fish-keeping, great care is still needed to prevent your fish from falling ill or even dying from lack of oxygen or from foul water. Remember, a single fish, one inch long (excluding tail), requires a minimum of one gallon (3.8 liters) of water to swim in. To keep water oxygenated, a broad-rimmed bowl should be kept full, while a spherical one is better left only half full. To avoid fouling the water, feed only what the fish can comfortably eat in two minutes. Uneaten food, together with the fish’s own waste products, will quickly pollute the water, which can in turn become depleted of oxygen. If your fish stops eating and starts gulping mouthfuls of air at the surface, this is an indication that the water should be changed immediately.

You should keep your fish bowl away from windows and direct sunlight (which promotes algae growth), and never stand the bowl where it’s likely to be in a draft. Fish are badly affected by sudden changes in temperature, which also means you should follow this step-by-step routine when changing the water.

Stand a bucket of clean water by the bowl overnight to allow the temperatures of the water to equalize. For the water, don’t use a bucket that has contained cleaning agents or other chemicals.

  1. A half-hour after feeding, net the fish and place it carefully into a small jar filled with water from the bucket.
  2. Empty the fish bowl and wipe the inside of it with a clean paper towel.
  3. Refill the bowl with water from the bucket.
  4. Carefully return the fish to the bowl.

Fish Tanks

Fish tanks are really the best receptacles for keeping fish indoors. The bigger the tank, the more fish it can hold and the slower its temperature will change. For most hobbyists, an aquarium holding 15 to 30 gallons (60 to 120 liters) is small enough to be easily cared for but big enough to make an impression, provide stability in water quality and hold a reasonable number of fish. A tank with a low profile shape, rather than a tall one, is preferable since it will provide a greater surface area for gas exchange. You can figure a tank’s capacity by multiplying length by width by height. If using inches, divide the answer by 1,728 to give cubic feet; 1 cubic foot holds 7.8 gallons. But don’t forget, a 15-gallon (60 liter) tank will weigh about 145 pounds (65 kilograms) when filled with water, gravel and decorations, so be sure the floor or shelf you’re using can support that kind of weight. Place the tank away from windows because temperature fluctuations are bad for the fish, and too much daylight will encourage algae to grow, cloaking the surface. Every tank needs a loose-fitting, nontoxic lid that will let in air but keep out dust. It will also prevent fish from jumping out and will retard water evaporation.

Plastic Tanks

Molded plastic tanks can make attractive small aquariums and have the advantages of no joints to leak, and plastic that’s unaffected by fresh or salt water. But, such tanks are rarely large enough to be of service as marine aquariums and when removing algae from the sides, the plastic is apt to scratch. Also, over time, the plastic will tend to turn yellow.

Angle-Iron Tanks

Angle-iron tanks are made from five sheets of glass fixed into a metal frame with putty. They are strong but can leak if the putty hardens and shrinks. They must be maintained by occasionally applying a sealant along the joints between the sheets of glass. If you’re planning to use such a tank for marine fish, the metal frame will have to be treated with anticorrosive bitumastic paint.

All-Glass Tanks

All-glass tanks are made from five sheets of glass glued together by transparent silicone rubber sealant. Strong, economical, nontoxic and providing the owner all-round visibility, they are the most popular choice among fish lovers. They must be stood on polystyrene sheets to prevent the bottom sheet of glass cracking beneath the weight of the water.

Essential Aquarium Equipment

Aeration System

It’s a very good idea to fit an aeration system to your tank. In these systems, a pump is used to force air down a tube that opens out underwater. The air passes through a stone diffuser that breaks it up into tiny bubbles, which dissolve into the water, oxygenating it. These bubbles also cause the water in the tank to circulate, pushing the depleted water to the surface where fresh oxygen can enter from the air above it. An aerated tank can support a bigger selection of fish without fear of suffocation – but you should always try to avoid overcrowding.


Filters provide a vital cleaning service in your tank. There are two basic kinds of these devices, mechanical and biological, each powered by an electric pump. It’s a good idea to fit both types to your tank. The mechanical filter will remove solid body waste, uneaten food and rotting plants, while the biological filter will rid the tank of harmful dissolved salts and will turn harmless wastes into substances that will feed aquarium plants.


A well-lit fish tank makes an attractive display and encourages plant growth. A 2-foot (61-centimeter) tank needs two 40-watt bulbs or, better still, one 20-watt warm white or a fluorescent tube. The lighting should be mounted under a metal reflector. Never illuminate your tank for more than 12 hours a day – your fish need their hours of rest every bit as much as you do!


If you want to keep tropical fish, the water must be heated to around 75 degrees Fahrenheit (24 degrees Celsius). Most heaters consist of wire elements sealed in glass or plastic tubes or in flexible rubber. The first type is laid above the gravel; the other is buried. Use one 100-watt heater for every 24 gallons (90 liters) of water in a normally heated room or a 150-watt heater in a chilly room. You’ll also need to use a thermostat and a thermometer to control and monitor the water temperature.


Thermostats control tank temperature and are wired in a series with a heater. They switch on as the water temperature drops and turn off when it reaches the set temperature once again. Some are housed in a tube that clips upright inside the tank, while others are clipped to the tank exterior.


It’s important to keep a regular check on water temperature to ensure the thermostat and heater are working properly. You can use a digital thermometer, one worked by a bimetallic strip or the familiar mercury type. These are usually attached to the outside of the tank in the form of a thin self-adhesive strip or attached inside the tank below the water line.

Water Plants

Every aquarium needs some plants because they help to oxygenate the water and will provide a more natural habitat for your fish. There are many different kinds of plants to choose from, and your choice will depend on the species of fish you intend to own, as certain species prefer different types of plant – so seek guidance before you buy.


Your tank will need a 2 1/2 to 3 inch layer of substrate material on the very bottom. Plants will root into it and various bacteria that break down harmful substances will live in it. It’s important to rinse the substrate in running water before placing it into the aquarium. You can also opt to use a special slow release fertilizer to aid plant growth.

Pebbles and Sand

A 2 1/2 to 3 inch layer of lime-free, smooth quartz pebbles should be carefully layered over the substrate to entirely cover it. If you prefer, you can use brown lava gravel or black basalt splinters, but avoid these sharp-edged types if you intend to keep fish that burrow, such as catfish.


To add the finishing touch to your aquarium, you’ll want to add some kind of decoration. Many fish owners like to place a realistic background in or behind their tank. You can buy relief backgrounds that can be fitted into the tank, as well as color photographic backgrounds that attach externally. Whatever you choose can be supplemented with rocks, stones, driftwood or pottery tubes and caves.

Now for the bad news. You need to wait two weeks before adding your fish. It will be maddening, but you must steel yourself and try to be patient. When you do purchase your first fish, don’t buy a load of them and add them all at once. Start with a couple, wait a week or so, then add a couple more. It’s a good idea to perform a partial water change before the addition of each new fish. Slowly build up the population until you feel the balance is right. Remember, don’t overcrowd them!

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