Bill, you are correct about how sensitive the fish are. In the summer, I can walk to the feeder and the fish can "hear" me walking. They start swimming to the feeder because they know I will throw out a couple handfuls of food.

While I still have ice on the pond, I can do a test. There is open water to the shore in my pond from the winter diffuser. I have 7" ice on the pond away from that open hole. I can take a 10' piece of PVC pipe, hang my O2 meter sensor from it and take an O2 reading. Then I can take readings away from the open water all across the pond.

My question to you is at what water depth do you think I should test the O2 concentration in the open hole? I will have to take the sensor to the PVC pipe and hold it out from shore. I have depth markings on the sensor cable.

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3/4 to 1 1/4 ac pond LMB, SMB, PS, BG, RES, CC, YP, Bardello BG, (RBT & Blue Tilapia - seasonal).