The hobby of keeping tropical aquarium is the maintenance of a highly artificial and restricted community of animals and plants, with a balance that can easily topple with disastrous results to at least some of the members. At the same time, aquariums can generally be easily maintained as long as a few fundamental facts are recognized and applied with common sense to the problems that arise.

The old-fashioned fish bowl has almost completely replaced for serious fish-keeping by the rectangular glass tank, either made wholly of glass or with a metal frame and glass sides and a bottom of glass, slate, or other rigid material.

Except when used for spawning, for exhibition purposes, or as a hospital tank for the treatment of disease, the tank contains growing, rooted plants; these are set in a sand or gravel layer 1 or 2 inches thick. There may be decorative rocks, but the chief decoration is usually the plants themselves, which contribute more to the attractive appearance of a well set-up tank than do the fishes.

Rectangular tanks are usually between 5 and 25 gallons in capacity; a 15-gallon tank measures 24 X 12 X 12 inches and is a favourite size. Smaller tanks than these cannot house many fish or allow proper development of the plants.

Size for size, most tropical fishes can be crowded a good deal more than the common goldfish and very much more than fancy varieties of goldfish. A 15-gallon tank might comfortably contain a dozen 3-inch rosy barbs, four or five 3-inch common goldfish at the most, and not more than a pair of Orandas of the same size.

Fish consume solid food and excrete solid faeces. They breathe oxygen and exhale carbon dioxide, and therefore they tend to deplete their environment of oxygen and to pollute it with carbon dioxide and excrement. Hence, the existence of plants is of extreme importance in the oxygen cycle.

You have to keep the water in your aquarium clean and aerated, the fish have to have enough food, if you use live plants, they will need light and nutrients, and you have to keep the algae under control.

If you’re just starting out, you need to know what you need to buy to get started. Here’s a list of the essentials that you need, no matter if you keep saltwater or freshwater fish:

An aquarium – To keep you fish in.

An aquarium stand – To support your new aquarium.

Filtration equipment – Filters can be chemical, mechanical and biological.

Lights – To help live plants grow, and to enhance the colours of your fish.

A tank hood – To reduce evaporation, and stop anything (such as a cat’s paw) from getting in.

Decorations – These can be anything you decide. There are a wide range of decorations available nowadays, so you can decorate your tank however you like. You’ll also want a background to hide the wires.

Substrate – This is basically the sand or gravel you use for the bottom of your aquarium.

Plants – There’s a wide range of plants you can choose for your aquarium nowadays, including live and plastic plants.

Heater – Tropical fish require a water temperature that is slightly higher than most people’s room temperature.

Chemicals – By chemicals, I mean chemical filtration, which gets rid of harmful gases that the water picks up as it passes through a carbon filter. It’s not always needed, but it is very easy to use and it’s better for your fish.

Thermometer – the plastic strip one with liquid crystals are best.

A net – For scooping things out of your aquarium.

Cleaning supplies (such as a scrubby on a stick, a small round brush

and a bucket reserved solely for aquarium use)

Fish food – to feed your fish, obviously.

And last, but not least… you’ll need the fish!