if i was to build an acrylic tank 54"L x 36"W x 24"T how thick would the acrylic have to be? could i use 1/2" or would i still have to use the 3/4"? and that would be roughly 200 gal. correct? im not building it yet but will probably by this spring or summer. also could i possible buy one for less $$$? new or used would work but id like to stick close to the sizes i have listed. thanks -jordan