esshup: The diffusers are grouped together. The air supply line is 3/4 Pex, the diffusers are in about 6' of water. The diffusers are from Environmental dynamics and are 9" FlexAir Threaded Disc Diffusers

The 1/2 HP surface aerator is in about 4' of water and suspended about 12" below the surface. Its creating a nice plum of water but unfortunately it doesn't look like my reading are good.

The meter is new, it is a MW600. I calibrated and zeroed the meter using the open air method as the manual instructed. I was getting a reading out of the water of 8.2 and did allow the meter to settle down before taking a reading. When taking readings from the pond I placed the meter at the various depths and then waited about 15 seconds for the reading to stabilize.

Both systems are running 24/7. The surface aerator was just added last Friday.