I can say I have done my fair share of kitchen remodels, the house Im in now was a fixer upper and the kitchen had to be completely gutted. Enjoyed it the first few times. But I have never built a pond before, the liner could be punctured, the lady has been telling me its looking like its losing water but I never paid much attention to it.
I would basically be doing it for the experience to have the pond the way I would want it, and expand it. And do some more higher end type filtering/plumbing underground.
I honestly believe my water quality is not that bad, so I would just pump it into a secondary container. The bottom has so much gunk and build up its just nasty and I literally clean the filter box everyday.
We had a relative who was doing some landscaping and I guess he was checking out the pond and was scooping up the bottom thinking he was doing something good for us. I noticed some pretty nice mossy black thick piles around the pond, maybe he stirred up some bad stuff, I seen in here someone saying something about that.