Theodore, before I forget, here is Addy's Bog Building thread. You will understand lots about bogs, and their filtration benefits for a pond. I hope this link works!
http://www.gardenpon...__fromsearch__1
My bog is simply part of my pond, but separate, too. I have a wall between bog and pond, and the water goes through the pea gravel (which fills the bog) and then is pushed up through all the roots of the bog plants, feeding the plants and filtering the water, then flows back into the pond. My computer is not cooperating right now with downloading pics, but you can look at my thread, too, for lots of pics during the construction and how the PVC pipes go together for the filtration through the bog.
https://www.gardenpondforum.com/top...es-2nd-pond-goldfish-only/page__fromsearch__1
Yes, by all means, if you have a lumber yard or place where building materials are sold, ask them about buying your EPDM liner. Yes, it IS going to be expensive, as the larger the piece, the more expensive it will be. BTW, the larger the piece, the heavier it will be, too! I moved mine into the ponds myself, but I used my tractor and loader to get the bundle to the pond edge. It's not something you can put in a wheelbarrow and move either! But, it's worth the money you spend to know it will keep your fish and plants safe for many many years to come.
Here's another thread you may be interested in if you want any other plants in and around your pond besides lilies. Addy put this one together, too, and did it very well.
http://www.gardenpon...__fromsearch__1
