It was most likely acrylic. Garf.org has some info on how to build your own tank. Basically you need to either buy precut sheets that you glue together or you have to cut the acrylic your self. The edges need to be pretty square and cleanly cut, so if you cut it yourself you need some decent tools - table saw with plastics blade and a router at least. The gluing itself is a bit of an art and takes some practice.
Filtration and heat depend on the size of the tank, lighting and what your plans for the tank are: Reef, Fish only, Fish only with live rock.
BTW Acrylic is also prone to easy scratching.
