Glass fish tank
Glass panes and metal frames were used in earlier aquaria. The containers were made watertight by coating the joints with pitch. Later tar was introduced as the sealant. In such containers, the metal frame took much of the stress and there were frequent leaks.
With the advent of silicone the joints between the glass pane became firm and all glass containers could be made. In some aquariums the metal frame is retained for purely ornamental and aesthetic reasons.