and as Bderik said about smaller 55 gallons being built with 1/2" glass its because its taller not long but tall and if u go over 18" tall u need 3/8" and if u go 21" or more tall u need 1/2"
or something like that lol not exactly sure the measurments but the taller u go the thicker the glass needs to be there fore im going the tallest i can with 1/4" with the proper bracing