The need for additional aeration is usually seen first thing in the morning.
The algae and submerged plants use oxygen overnight as do the fish, and as a
result oxygen levels are their lowest around sunrise. The fish will tell
you they need more oxygen by piping at the surface, gulping air and water to
try to get extra oxygen. If the fish are down and acting normally, then
there is not an oxygen problem to worry about.
--
RichToyBox
http://www.geocities.com/richtoybox/pondintro.html

"DD DDD" wrote in message
...
Hi, When I look at the bell at night with the pond light on it looks
like a lot of air bubbles going down into the water and rising. But I
was checking to see if there is a better one for air. Or is there
something I can add to the pump/filter to add more air to the water,
without using a air pump? Or should I add a air pump? Thanks all