Tanks are sold in many shapes and sizes, but they are only made of two types of material: glass and acrylic. Here are some advantages and disadvantages of the two types:
low refraction (distorts less at angle)
tank support at edges
entire base needs support
easier to clean
abrasives causes scratches
Perspex is used occasionally in place of acrylic. Most of the comments that apply to Acrylic apply to Perspex.
Glass aquariums are held together either with a metal frame or a special super-strong adhesive.
Aquariums are sometimes found that are molded entirely of one piece of glass. These aquariums often have unsightly bubbles in the sides of the tank. They shatter relatively easily. They tend to distort the view of the fish at certain angles.