Having that thick ice near the hole is normal. I've measured ice thickness in my pond and it was uniform until I got within 20 feet of the open hole, then it dropped an inch in thickness. I was drilling a hole every 10' as I approached the open water.

Here is a picture of my pond from today. The hole is about 40'-50' diameter.

Here is a close up of the plume coming from the single diffuser.


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