Design and shape of the aquarium
Long and narrow, high and short, aquarium just made of glass or with a frame?
As with the size, the shape of your aquarium may be more than just a matter of taste. Fast and frequent swimming fish need longer aquariums than quiet fish species, such as discus fish which instead require a larger amount of aquarium height and depth. Please ask your specialist shop for advice regarding the demands of your "desired" fish and the aquarium format needed.
When aquariums were „invented“ they were made of a metal frame with glued in panes. Thanks to the current high quality adhesives, frames are not necessary anymore, but can still be found for decorative purposes. So it is entirely up to you to decide on your design.