aquarium

Tank or similar container used for the study and display of living aquatic plants and animals. The same name is used for institutions that exhibit aquatic life. These have been common since Roman times, but the first modern public aquarium was opened in Regent's Park, London, in 1853. A recent development is the oceanarium or seaquarium, a large display of marine life forms.

Freshwater fish The easiest types of fish to care for in an aquarium are coldwater species such as the goldfish (Carassius auratus). More complicated is the keeping of tropical freshwater fish such as the angel fish (Pterophylum species), Siamese fighting fish (Betta splendens), and guppy (Lebistes reticulatus). For these a water heater with a controlling thermostat is required and usually a filter and aerator powered by a small electric pump. There is usually a sand or gravel substrate in which ornamental plants are grown to assist in aerating the water.

Marine fish Even more complicated to keep are tropical marine fishes. These usually have to be kept in artificially made sea water, again heated by a thermostatically controlled submersible heater. Since plants will not survive and very soon decompose in sea water, a filtration system is absolutely essential. Most of the marine fish are very delicate and require great care. Examples are clown fish (Amphiprion species), butterfly fish (Chaetodon species), and the Moorish idol (Zanclus cornutus).

Other water creatures Also kept in aquaria are common pond creatures such as carnivorous water beetles (Dytiscus), water boatmen (Notonecta), water snails (Lymnaea and Planorbis), and dragonfly nymphs.