On Sat, 7 Jun 2008 20:17:15 EDT, "Pat"
wrote:

My question is this: If, as I understand it, the pond needs oxygen in the
water to keep from stagnating and to support fish, and if certain plants are
generally used for this purpose, and if one needs a liner in the pond to
keep the water from seeping back into the earth, how are the plants to take
root? Obviously they can't get any nourishment from the pond liner and would
damage it if the roots penetrated it.

Garden ponds usually have liners to hold the water. There are more
than one kind. The preformed plastic was the one I started with, but
soon learned about 40 mil EPDM (like rubber) and I prefer that type
now. Without a liner the pond would continually remain cloudy, since
goldfish and koi were both bottom feeders and suck up dirt and spit it
out looking for food in the bottom mud.

Water can be oxygenated by spraying it into the air or dropping it
from a water fall, flowing it down a stream or even pumping a stream
through the water generates some oxygen. Mud bottom ponds (usually
measured in acres) are often oxygenated by spraying the water into the
air and let it fall back into the pond.

Plants during daylight hours absorb carbon dioxide and release oxygen,
but at night when sunlight is not available for plants to use to make
plant food, the plant takes oxygen from the water and releases some
carbon dioxide. This doesn't mean that plants aren't beneficial, they
are and more ways than just oxygenating the water. They absorb fish
wastes as plant nutrients helping to clean up the toilet bowl
existence of the fish pond. There are many plants that fish keepers
use, but the most popular are probably fast growing floaters, like
water hyacinth, water celery and several others. That is not to
discount the value of many others that require an anchor to keep them
in place. I have Louisiana iris anchored to cinder blocks, their
roots attach themselves to the heavier blocks and keep them upright in
winds. Rush and canna lilies also work well as cleaners in some
ponds, but the canna grow tall and blow over in the wind in my pond.

I don't consider my potted lilies an oxygen producing or cleaning
asset. I fertilize the lilies so they will bloom well, look good and
shade the pond as well as providing a cover for the fish. I feel I
should point out the fish will root around in plant pots and vacuum
the dirt up blow it out and leave the water cloudy if the pot surface
is not covered with stones the fish can't pick up and move.
--
Hal Middle Georgia, Zone 8
http://tinyurl.com/2fxzcb