I once did some research on building
and maintaining ponds for folks of limited
Having both the pump and the filter out
of the pond was the best setup for these
folks. Also using velcro closings and anything
to ease the opening of various containers,
dividers, etc. worked well.
I think Jan's filter would be a good option.
Also a skimmer and bottom drain.
all of which jj includes in her pages.
My article was published by the now defunct
Pond and Garden, though I think it is still available
on a CD they put together of all their issues.
Go here http://pondandgarden.com/
(disclaimer - no monetary compensation comes
my way from this CD ;-)
good luck with your parent's pond and let
us know how it goes!