O2 enters water by its contact with it. So with that said the more surface
area you have for air to contact the water the quicker O2 can be
(re)absorbed. However, once the surface water is saturated with O2 no more
O2 will be absorbed in the pond. Very little O2 is added to water via the
air that comes out of an airstone. It's main purpose is to agitate the water
surface and create current so that the saturated surface water that was
exposed to the air drops and O2 depleted water raises to the surface.

If you had an airstone that made it so that there were always 1,000 bubbles
with a size of 1/32 of an inch in your water you'd only be adding around 12
square inches of surface area to your pond. That's a 3"X4" square.

If you have a pump that's creating current in your water you're fine. Now
using a fountain is a great way to get O2 in the water because you're
generating a HUGE amount of surface area because the water is being blown
apart into droplets and wrapped around by air. You'd be better served though
to have the pump for the fountain at the bottom of the pond. If it's input
is at the top of the pond you're saturating water you just saturated.

This is why those big air stone disks for rec ponds work so well. Ponds less
then 8-12 feet don't stratify (meaning there is no current caused by
different temperatures of water raising and failing). The disks are placed
at the bottom of the pond and make a current that takes the low O2 air at
the bottom and pushes it to the top of the pond to get saturated.

Sam


"FBCS" wrote in message
...
I have read lots have natural ponds/VG filter no falls and they do not
talk
of the need for an air pump/stone. How necessary is a air pump/air stone
to
the health of the pond? Do you calculate size by gal with this type of
pump
also. If not what would be a typical size for a pond, better yet, what do
you use? Joann