"BenignVanilla" writes:

"Lee Brouillet" wrote in message
...
BV, if I had the *slightest* idea of how to explain barometric pressure, I
would. Unfortunately, I can't. But maybe someone else can . . . How it
works
is something else: as the bubbles rise, they displace the water. New water
moves in to replace the air bubbles, and pulls the "stuff" with it,
drawing
it more towards the drain. The oxygen benefits of the air diffuser is
pretty
much self explanatory. Folks that had regular covered bottom drains and
upgraded to the "air domes" swear by them.
snip

So the bubbles don't go into the drain, they surface above it. That makes
sense...not sure I want my pond constantly bubbling though.

Me too, that's why I aerate in the filter with a spray bar. No additional
air pump required either.