We have an 11x16 Aquascape pond that is about 3 1/2 years old. We
started having issues with the pond not filling to capacity and
couldn't find the leak. I also wanted the pond to be a little deeper
so I decided to remove the old liner, dig a little, and install a
larger liner (the original liner from Aquascape was, in my opinion, too
small). Shortly after starting the replacement, I discovered a spot
that was overflowing (partially because of the borderline original
liner size). I figured this was the problem but couldn't locate it in
my previous search attempts. Anyhow, on to the fun stuff.

Rocks lining the pond... If I had to install a pond again, I would
definitely NOT use rocks to line the pond. First you have to have
several thousand pounds of stone delivered (expense) and then you have
to install it (plenty of work). Down the road, if you decide to make
changes like I did, you (obviously) have to remove several thousand
pounds of stone/sludge and then replace several thousand pounds of
stone. I'm actually going to put my stone back in our pond simply
because I have to do something with it.

Lily pads... One of the most incredible root systems that I've ever
seen in my life. There was literally an alien body in my pond which
words cannot adequately describe. A several hundred pound mass of
roots and rocks about 8 feet long and up to a foot and a half thick.
It was simply amazing. We had to cut it into pieces just to remove
it... roots, rocks, and sludge. And here I thought I was imagining
things when I thought my pond wasn't as deep as it used to be. Has
anyone else seen this?

Anyhow, just thought I'd share my experience and previously undecided
opinion on rocks as a liner material (no longer undecided on this
issue).