Quote Originally Posted by drache View Post
if I put the largest cage on top, it needs to be lighter than a glass tank would be - particularly one with sliding doors, which it would also have to have
wood would also be too heavy
Plywood. I made a 110 x 70 x 50 cm plywood terrarium a couple of years ago. I made a frame of 21 x 21 mm wood and covered the whole damn thing with 4 mm plywood and made swinging polycarbonate doors. The terrarium ended up lighter than the 460 x 577 x 6 mm sliding glass doors on the terrarium it replaced. The only way to make it lighter than that, would be to replace the plywood with fabric or very thin plastic.