Well the results of my O2 are in. At 5:00 P.M. My DO levels were 8ppm at the surface and 6ppm at 5 ft. I don't know about 12 ft. Since this was in the evening I can assume that the DO levels were at a high point of the day. Is this enough DO or can it go down to critical levels at night. I put my sump pump going and I rigged a PVC fountain in the middle that is shooting water about 10 feet in the air and about 10 feet in all directions. Should I continue to aerate from the bottom diffuser or just go with the fountain for a while? It is creating a nice ripple on just about the whole pond except for 1 corner, so I think this is going to help with O2 and my algae problem. I had this fountain going for about 2 hours before my DO was read. How fast does DO levels go up? I should have had the DO read before I turned the fountain on. I bet the DO levels were somewhat lower before the fountain was turned on.