What's (structurally) a safe tank..buying...and buying 'used'
This comes up now and again---somebody trying to buy a used tank.
Acrylic or glass---both kinds of tanks have their cautions.
Acrylic scratches easily, grain of sand getting stuck under a magnet scraper---glass not so much.
Acrylic unsupported by bracing can, over years, bow outward with the heat and weight of the water and sand. You can deal with this, generally, but do be sure that the acrylic is thick enough...