connecting 2 ponds-need tips from those that have done this!

Hi,

Well I am adding a 220 gal pond to my 100 gal older one and I would
appreciate any tips or suggestions you may have. Please take a look at this
picture http://funjax.com/pond . It shows the new pond in a half dug hole,
close to the position I want it to be. My thoughts on how to proceed are
this, cut both ponds about 6" wide from the top down to about 2" above the
plant shelf. Take EPDM and put it between the 2 ponds gluing it to the sides
and bottom of each pond. Then adding a hose to the intake valve of my 1800
GPH pump that feeds the waterfall and run the intake hose to the far end of
the new pond. I do have one specific question, what is the best adhesive to
use? Thanks for any suggestions you have! Larry