RC, the lime road rock works well by adding the calcium you need with all your pine trees. Only problem might be when a bigger rain event comes the smaller rock will likely wash into your pond.
if your inflow areas are fairly level, I would opt for 10-12 inch lime rock as it is more likely to stay in place. You will get the same benefit of the additional calcium, plus filtering a lot of debris out and 100%+ DO saturation.
I have a pond "in the woods" in a steep draw (8:1 slope) and I had a mini-dam built out of Dolomite Limestone. The run-off hits it and flows through filtering out tons of hardwood leaf debris and keeping my PH around 7 (PH was ~5 prior to rock filter dam).
The rock works well but may not be attractive in many cases.
