Materials:
Most aquaria consist of glass panes bonded together by silicone, with plastic frames that are attached to the upper and lower edges for decoration. The glass aquarium is standard for sizes up to about 1000 litres (250 gal). However, glass as a material is brittle and has very little give before fracturing, though generally the sealant fails first.[26] Aquaria come in a variety of shapes such as cuboid, hexagonal, angled to fit in a corner (L-shaped), and bow-front (the front side curves outwards).[27] Fish bowls are generally either made of plastic or glass, and are either spherical or some other round configuration in shape.The very first modern aquarium made of glass was developed in the 19th century by Robert Warrington.[28] During the Victorian age it was common for glass aquaria to have slate or steel bottoms, which allow the aquaria to be heated underneath with an open flame heat source. The aquaria back then had the glass panels attached with metal frames and sealed with putty. These metal framed aquaria were still available on the market until the mid 1960s when the modern, silicone-sealed style displaced them. Acrylic tanks were not generally available to the public until the 1970s.
Although glass aquaria are usually preferred by aquarists over the acrylic ones because of their resistance to scratching and much more accessible price, they come with several disadvantages. Not only are they not as crack resistant as acrylic tanks but they are also nearly two times heavier than the latter. They also provide less insulation than acrylic aquaria and do not come in as many interesting shapes as these do.[29] Many aquarists or beginners who want to get fish as pets find it particularly onerous that many online suppliers will not ship glass aquaria because of the high potential for cracking and the high weight, which increases the cost of shipping. However, glass tanks are more convenient for other aquarists because unlike acrylic, glass does not yellow over time, and also because glass tanks do not need as much support as acrylic aquaria.
Even though the price is one of the main aspects which is taken under consideration by aquarists when willing to purchase one of these two types of aquaria, when it comes to very large tanks the price difference tends to disappear.Acrylic aquaria are also available and are the primary competitor with glass. Acrylic aquariums are stronger than glass, and much lighter.[30] Acrylic-soluble cements are used to directly fuse acrylic together (as opposed to simply sealing the seam).[26] Acrylic allows for the formation of unusual shapes, such as the hexagonal tank.[15] Compared to glass, acrylics are easy to scratch; but unlike glass, it is possible to polish out scratches in acrylic.[26]
Laminated glass is sometimes used, which combines the advantages of both glass and acrylic.[26]
Large aquaria might instead use stronger materials such as fiberglass-reinforced plastics. However, this material is not transparent.[26] Reinforced concrete is used for aquaria where weight and space are not factors. Concrete must be coated with a waterproof layer to prevent the water from breaking down the concrete as well as prevent contamination from the concrete.[26]
Styles:
Aquariums have been fashioned into coffee tables, sinks, and even toilets.[31][32] Another such example is the MacQuarium, an aquarium made from the shell of an Apple Macintosh computer.[33] In recent years, elaborate custom-designed home aquariums costing hundreds of thousands of dollars have become status symbols—according to The New York Times, "among people of means, a dazzling aquarium is one of the last surefire ways to impress their peers."[31]
A kreisel tank is a circular aquarium designed to hold delicate animals such as jellyfish. These aquariums provide slow, circular water flow with a bare minimum of interior hardware, to prevent delicate animals from becoming injured by pumps or the tank itself.[34] Originally a German design (kreisel means spinning top), the tank has no sharp corners, and keeps the housed animals away from the plumbing. Water moving into the tank gives a gentle flow that keeps the inhabitants suspended, and water leaving the tank is covered by a delicate screen that prevents the inhabitants from getting stuck. There are several types of kreisel tanks. In a true kreisel, a circular tank has a circular, submerged lid. Pseudokreisels have a curved bottom surface and a flat top surface, similar to the shape of either a "U" or a semicircle.[35] Stretch kreisels or Langmuir kreisels are a "double gyre" kreisel design, where the tank length is at least twice the height. Using two downwelling inlets on both sides of the tank lets gravity create two gyres in the tank. A single downwelling inlet may be used in the middle as well. The top of a stretch kreisel may be open or closed with a lid. There may also be screens about midway down the sides of the tank, or at the top on the sides.[36] It is possible to combine these designs; a circular shaped tank is used without a lid or cover, and the surface of the water acts as the continuation of circular flow. It is now possible to start a jellyfish aquarium at home as easily as a regular fish tank.[37]
Another popular setup is the biotope aquarium.[38] A biotope aquarium is a recreation of a specific natural environment. Some of the most popular biotopes (to name only a few) are the Amazon river,[39] Rio Negro River, Lake Malawi,[40] Lake Tanganyika, and Lake Victoria. The fish, plants, substrate, rocks, wood, and any other component of the display should match that of the natural environment. It can be a real challenge to recreate such environments and most "true" biotopes will only have a few species of fish (if not only one) and invertebrates.
Aquarium size and volume:
The large Georgia Aquarium houses a whale shark.
Lisbon Oceanarium designed by architect Peter Chermayeff
Unfiltered bowl-shaped aquaria are now widely regarded as unsuitable for most fish. Advanced alternatives are now available.[41] Aquariums should contain three forms of filtration: biological, mechanical and chemical to keep water conditions at suitable levels.
Reef aquaria under 100 litres (20 gal) have a special place in the aquarium hobby; these aquaria, termed nano reefs (when used in reefkeeping), have a small water volume.[citation needed].
Practical limitations, most notably the weight (one litre of fresh water has a mass of 1 kilogram (8.3 lb gal−1), and salt water is even denser) and internal water pressure (requiring thick glass siding) of a large aquarium, keep most home aquaria to a maximum of around 1 cubic metre in volume (1,000 kg or 2,200 lb).[27] Some aquarists, however, have constructed aquaria of many thousands of litres.[42][43]Public aquariums designed for exhibition of large species or environments can be dramatically larger than any home aquarium. The Georgia Aquarium, for example, features an individual aquarium of 8,100,000 US gallons (30,700 m3).
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