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.
--
RichToyBox
http://www.geocities.com/richtoybox/pondintro.html


"Mike (mixmanx at AV and DVD Forums)"
wrote in message
. ..
Hi,

I've just finished building a small pond using a liner, but I'm not sure
if
it's a good idea to put gravel in the bottom or not. Being a tropical fish
keeper, it seems the natural thing to do, and I think it will look better,
but will it be a pain to keep clean?

Any thoughts much appreciated.


Mike