Hi Steve,
Thanks so much for you post!  I have been thinking about this quite a bit the last little while and yes, I am caving to the thought of having to use glass for the bottom.  I really like the idea of PVC but am just not sure of the implications at this point to go ahead with it…not thinking with my heart here, just my brain.  I have had to put the tank build on hold for the moment, 

 hopefully only a month or two but Denise at Golds has assured me that he will be able to help me and since they have always been the most knowledgeable and helpful, I think I will give them my business for this as well.  I am hoping to post up my design in a month or so to get some feedback!
Cheers,
Theresa