iani said:
When an acrylic tank starts to bow the downwards pressure becomes uneven. You get an increase of pressure along the vertical walls that are bowing. If the foam gives even the slightest you will get an increase in the bowing. It is much better to have a solid bottom than a semi rigid bottom.
I thought about that before, and thought about it even more after your post.
I really think that is backwards.
As the front bows out, the square tank becomes more like a tube.
The front bowing out should actually pull UP slightly on the front lower walls.
The tension from the outward pressure does it.
(It pulls down on the top though)
EDIT:
That last statement got me thinking even more.
As the top of the tank drops drops down relieving the tension mentioned above,
it would really reduce that force.
So most of what is left would be the simpler (but seemingly weaker) leverage force.
Basically, as the front moves outward, it puts torque on the joint with the bottom, causing
it to twist downward.
But it sure seems that the force from that torque should be minor as things flex.
Complex. I guess it all depends on how the tank is built.