The bottom does not need to be as thick as the sides or top because for acrylic, the entire bottom has to be supported by a solid surface. Glass tanks are supported by the perimeter only but acrylic will fail if kept on a glass tank stand for long term.
The top needs to be thicker, for the above application I would use a top of at least 1.25 inches thick and make sure all the openings in the top have radiused corners and not 90 degree angles as that creates a stress point and will form a crack.
FWIW.