Pine Tar,

I use an auger to "plant" structure in pond construction jobs all the time. I use quikrete in my holes, just pour it in dry and mix it up soupy with water in the hole. If you have a good clay bottom all the way to the bottom of your hole, you can pack back with clay. If not good clay, you could run the risk of a seep. The soupy concrete is a safer bet to seal, and in my opinion easier than trying to pack clay @ whatever you stick in that hole. I normally put varying amounts of structure from 3' -10'. Adding aeration to the deep water will open up more of that area of the pond to more fish for a much longer time of the year, so you may want to put some structure at those depths. I would still focus my efforts more on the shallower depths. The Vertex bottom diffuser systems (which I sell) are very high quality and should be able to accomplish what you are trying to do.

-HH