I love this idea, that way I could get huge tank space and a pond. This way the wife couldnt complain about how much space the hobby consumes.
I think the only thing I would do differently is the supports for the tank, not to be negative but 4x4's tend to sag and twist, but two 2x4's screwed together would be just as strong with a much smaller likelihood of twisting or bowing. Just a suggestion. Thank you for this idea, I will be doing something xtremely similar next spring.
Keep the updates coming, and if you dont mind could you let us in on how much the project cost?