Modern fishkeeping

Marine aquarium components:

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The major components are an aquarium, usually made from glass or acrylic, filtration equipment, lighting, and an aquarium heater. Marine aquariums can range in volume from less than 80 litres, (< 20 US gal) to over 1,200 litres (300 US gal). Small volumes are more difficult to maintain due to the more rapid changes in water chemistry. The majority of saltwater aquariums are between 160 and 400 litres (40 and 100 US gal).

Nano reef aquarium maintained at home

Types of marine aquariums

Marine aquarists typically divide saltwater aquariums into those housing fish only, those housing fish with live rock, and those primarily designed to house corals and other invertebrates (also known as reef aquariums). Many fish hobbyists also divide the types of saltwater tanks based on the water temperatures at which they are kept.

Tropical marine

The most common type of saltwater fish tank, the tropical marine tank, houses marine animals from tropical climates. Usually kept between 24 to 28 degrees Celsius (76-82 °F), these tanks include tropical reef tanks, as well as fish-only tanks. These tanks tend to have a low concentrations of microscopic plankton and other foods eaten by filter feeders. Most livestock for these aquariums are acquired through commercial means.

Temperate marine (cold water marine):

A temperate marine aquarium

One of the more obscure types of fish tanks, the cold water marine tank, holds fish of temperate climates, with temperatures ranging around 10 to 24 degrees Celsius (50–75 °F). While most of these tanks are not as aesthetically pleasing as their tropical counterparts, colorful species such as dahlia anemones and the ornate cow fish can be found. However most cold water fish are gray or dull in color. Most colorful species are found in the western pacific. These tanks also tend to require extra skill to maintain.
Since cold water cnidaria are rare and cold water corals only occur at great depths, hobbyists are largely confined to fish, crustaceans and mollusks. Since there are very few commercially available cold water fish, hobbyists usually have to physically acquire specimens. The most common way of doing this is by trolling or seining. Unlike commercially available tropical fish, whose behavior patterns and tank compatibilities are well documented, cold water fish require much local ichthyology knowledge in order to maintain them.
Many temperate fish have specific local diet requirements, while others, like tautog (black fish), will eat just about any crustacean or frozen foods. The black fish should not be kept with crabs and mollusks, while other fish, like the oyster cracker toad fish, will do fine with any fish that is not small enough to fit into its mouth. Due to it being such a localized hobby, not many people go the route of local tanks. However, they are more cost-effective than reef tanks, cheaper and easier to maintain, and the fish hardier. It takes experience before one can successfully Gage the compatibility of the fish in one's area.

 Live rock:

Main article: Live rock

Live rock is rock that has been in the ocean, composed of limestone and decomposing coral skeleton, usually around a coral reef such as those around Fiji, and is usually covered with beneficial algae, coralline and tiny invertebrates and bacteria that are desirable in the aquarium. Some examples of the microfauna commonly found on live rock are crabs, snails, feather dusters, brittle stars, starfish, limpets, abalones, and an occasional sea urchin, sea anemone, coral, and sea sponge. Also, if the aquarist is unlucky, a mantis shrimp. Bristleworms are also common, most of which, while unattractive, are not harmful and are useful scavengers; some species can be pests, however. The addition of live rock is one of the best ways to ensure a healthy aquarium, as the rock provides a buffer to maintain high pH (8.0-8.3), alkalinity, and acid-neutralizing capacity. Alkalinity is often known by a rather confusing term, "carbonate hardness", or KH. This is usually measured in "degrees" (dKH) or meq/L.
The microfauna found on live rock are detrivores and herbivores (as they eat algae and fish waste), and provide fish with a natural, attractive shelter. Live rock usually arrives from online dealers as "uncured", and must be quarantined in a separate tank while undergoing the curing process, which involves the inevitable die-off of some of the rock's inhabitants and the subsequent production of undesirable ammonia and nitrite. Live rock that is already cured is available at most pet stores that cater to saltwater. Live sand is similar to live rock and is equally desirable.