A saltwater aquarium is a contained aquatic environment within which marine plants and animals are maintained. The peculiarities and limitations of seawater, along with the special needs of marine plants and animals, make a saltwater aquarium much harder to maintain than a typical freshwater aquarium. However, even the most die-hard proponents of freshwater aquaria admit that freshwater fish and other sea life pale beside the spectacular appearance of many of their saltwater kin. In addition, the sheer variety of saltwater creatures that can be kept in aquaria far outstrips what can be kept in most freshwater setups. It should be noted that saltwater life, require the utmost care and maintenance.
There are of course practical limits to saltwater aquariums, even for those with extremely high budgets. Open-water and deep-sea environments are quite impractical and nearly impossible to recreate in the confines of one's home aquarium. In addition, it can be just as hard to obtain creatures that live in such environments. It is however, possible to recreate a tropical coral reef in one's own living room, replete with corals, sea anemones and feather worms, and even such esoteric and more maintenance-intensive creatures as molluscs, seasnakes, shrimp and octopi.
A saltwater aquarium requires nothing less than an excellent filtration setup. Its water management program must be strictly adhered to as well. Seawater contains more dissolved solids and minerals than does freshwater, and marine fish, invertebrates and plants are far more sensitive to changes in water quality and temperature than their freshwater equivalents. In addition, an amount of seawater contains less oxygen than a comparable amount of freshwater, limiting the number of marine creatures that can be maintained per gallon of water. Therefore, water-related variables such as salinity, alkalinity, temperature, nitrate, nitrite, calcium, and pH levels must be watched closely. In support of this, efficient filtration mechanisms such as wet and dry filters, protein skimmers and related equipment must be used. The water should also be kept as clean as possible and therefore changed often and replaced with conditioned water.
Lighting is employed to help aquatic plants nourish themselves and to bring out the best appearance of the tanks inhabitants. Many sorts of lights are available, such as fluorescent, light emitting diode (LED), metal halide, and actinic lights.
A saltwater aquarium that exists in a colder climate may also involve some heating mechanism, especially if the animals and plants kept in them hail from warmer areas. Heating the aquarium is necessary to keep the water temperature at a habitable level. As with water quality, both lighting and heating systems need to be maintained with the utmost care in order to keep the saltwater aquarium's inhabitants happy and healthy.