hey I just started building my new tank, its going to be made out of landscaping timbers stacked lincoln log style with a rectangle cut out in the front. to secure the logs together im drilling holes in the corners and sticking a metal rod down there. then i'm going to line the inside (except for the window space, of course) with 3/4 plywood. after that I'll put a pond liner down in there, and cut out space for the window in that too. Finally, i have a 3/4" thick 2'X4' sheet of acrylic that I am sealing to the pond liner and bolting to through the plywood and into the landscaping timbers. should be 5.5 feet long, 2.5' wide, and 2.75' feet tall, but the functional area inside will be slightly less due to the thickness of the timbers. as soon as i get my 5 posts in i'll post up pics of what I have done so far, until then, any suggestions or comments are welcome! thanks.