McTeague, i used to install corian back in california. now i just install granite. more money
and yes, it is very rigid material. as for making fish tanks from corian, its just a bad idea all together. depending on how you fab the tank, it could very easily come apart from the seams once running. obviously that would be bad! the material is .5" thick, and pretty heavy. the material also expands and contracts with tempurature. if you dont take extra steps in beefing up all the joints, that tank probably wont hold up for very long. it doesmake an awsome counter top material though... i have seen it used to build an extremely large (1000g +) sting ray tank at the monterey bay aquarium, but it was all backed by concrete, so the water pressure forcing the corian walls outward really have no effect. im actually always afraid my tank will pop apart, but i dont think it will because i coved all the inside corners.