Aquaria

An aquarium, or aquaria in plural, is a closed or semi-closed container that houses aquatic plants and animals in a controlled environment. Aquaria range from small desktop tanks to large public displays and can be freshwater, brackish, or marine.

Most systems include a tank with a lid and stand, a substrate, decorative features, and a filtration setup that provides mechanical, biological, and sometimes chemical filtration. Lighting and heating regulate day–night cycles and water temperature. In many planted or reef aquaria, additional equipment such as CO2 systems or protein skimmers may be used.

Common types include freshwater community tanks with multiple compatible species, species-specific tanks, planted tanks that emphasize aquatic plants, biotope tanks that imitate a natural habitat, brackish tanks with intermediate salinity, and marine tanks, including reef aquaria that attempt to maintain corals and other invertebrates.

Maintenance centers on establishing a biological filter through a process called cycling, monitoring water chemistry, and performing regular water changes. Keepers test parameters such as ammonia, nitrite, nitrate, pH, hardness, and, for marine systems, salinity. Overstocking, overfeeding, and inadequate filtration can lead to stress and disease. Quarantine of new specimens is common to reduce disease risk.

Ethical considerations include humane treatment and responsible sourcing to minimize environmental impact. Public aquariums and research facilities use aquaria to educate visitors and study aquatic ecosystems.