Extruded will not hold up for aquarium use. It is typically used for point-of-sale material that will be thrown away. Extruded will craze (spider cracks) as it absorbs 40% more water than does acrylic.
Bite the bullet and get cast material. The US cast is best but expensive. If you purchase import cast, use Chemcast. However, I would not build an aquarium out of it.