Question
Do you know of Koi Carp, or Sturgeon causing holes in black beutile lining? The water drops all of a sudden then levels out and is topped up, then might be alright for some days, then it drops again. There is a waterfall in the pond, but the pipes have been checked and they are Okay. The liner has small holes in it, and was layed by experts. Thanks Alot.

Answer
The liner is Butyl rubber?  They are usually pretty good.  Koi won't put a hole in most pond liners.  I don't know much about sturgeon though so who knows.  Here is my section on leaks:
http://www.fishpondinfo.com/pcare.htm#leak
The level to which the pond drops is probably where the worst of the leaks are.  You actually see the holes in the liner clear through?  If so, I would ask for money back from the warranty of the liner or from the "experts" who put it in.  I'm not sure why are retopping the pond level would ok for a few days before dropping.  That part doesn't make sense.  Good luck!