Aquarium

An aquarium is a water-filled container or system designed to house aquatic plants and animals for display, study, or hobby purposes. Aquariums range from small desktop tanks to large public exhibits. They can be made of glass or acrylic and may be standalone units or part of a larger recirculating setup. Common categories include freshwater, marine (saltwater), brackish, and planted tanks. Freshwater aquariums keep freshwater species and can be tropical or cold-water. Marine aquariums maintain seawater and support corals and many reef organisms, which require stable salinity and specialized equipment. Brackish tanks blend freshwater and saltwater conditions for species adapted to intermediate salinity. Planted tanks emphasize live aquatic plants as the primary form of decor and often rely on high light and carbon supplementation.

Key components include the tank, stand and lid, a filtration system, a heater for tropical species, lighting, substrate, and decorative elements. Filtration provides mechanical, biological, and sometimes chemical cleaning and helps circulate water. Lighting supports photosynthesis for plants and influences fish behavior. Tanks must be properly cycled to establish beneficial bacteria that convert ammonia to nitrite and then nitrate before stocking.

Maintenance involves regular partial water changes, substrate cleaning, equipment checks, and monitoring of temperature and water chemistry. Avoiding rapid changes in temperature, salinity, or pH reduces stress on inhabitants. Stocking density and species compatibility are important to prevent aggression and bioload problems. Ethical care includes quarantine of new animals and sourcing from responsible suppliers.

Philip Henry Gosse popularized the term aquarium in the mid-19th century, and the hobby expanded through the 20th century with advances in filtration, lighting, and husbandry. Today aquariums range from simple educational displays to elaborate biotope and reef setups.