"RichToyBox" wrote in message
. net...
Mike,

The tropical fish tank has an undergravel filter that draws water down and
through the gravel. That works and works well. In a pond, the gravel is
just sitting there collecting dead leaves, dead algae, poop, and all
manner
of other things that are going to rot. Without the flow of water through
the gravel, the rotting is anaerobic, creating hydrogen sulfide gas that
is
toxic to the fish, provides a hiding place for parasites, and is a royal
pain when it comes time to clean the pond. The gravel does give the pond
a
more natural appearance, but the good blanket algae will grow on all
surfaces, and then the gravel will look like the liner, or vice versa.


Thanks, that's what I was thinking, it's just the liner has a few bumps and
creases in it due to the shape of the pond and I don't really want to see
them, but like you say, algae will form on there and it will probably look
ok.


Mike