Current placement of brushpiles is best for small fish cover / hiding places. For the vertical fence cylinders, I think clustering them together in large groups will be the best arrangement. Placed individually willnot provide much of a refuge area. Depth for fence columns should be just so tops are under water no more than 12"-18"; shallower is better. Sounds like you are making lure "grabbers". However I think "no fishing" areas are very beneficial in ponds.
