An aquarium is a glass-sided container in which water-dwelling plants and animals (usually fish) are kept in captivity.
The keeping of fish in an aquarium became a popular hobby during the twentieth century, with many species of fish being caught and transported from the tropics before it was discovered how to breed them. Freshwater aquaria remain the most popular form, but marine (saltwater) aquaria have gained cachet as the true enthusiast's preserve.
Aquaria can vary in size from a small bowl just large enough for a single goldfish to the huge public aquaria that can simulate entire marine ecosystems.
With the advent of Dutch Aquariums[?] and Takeshi Amano[?]'s photographs in Natural Aquarium World[?], aquatic enthusiasts began to take interest in aquatic plants in the 80s or 90s. The major technological hurdle was the introduction of CO2 gas into the fish tank, both to control algae, and to provide carbon for the growth of the aquatic plants.
