Tom,

Really shaping up as a great pond! The pictures will really help you remember where that structure was placed, if you are like most of us(or at least like me).

I can address a couple of the questions from my experience.

Regarding keeping the oak trees in place, I purchased several bags of the redi-mix concrete and placed them on the trunks of the trees I had moved into my pond. Cost $3 per bag or so and if you place them properly on the trunk, the branch end of the tree will actually suspend making terrific structure, very natural like. Other material could be used if you have it, but the concrete bags are very easy to place where you want them. To be double sure of keeping them in place you may want to tie them on to the trunk with some rope. My trees were not huge, however and if yours are very large, this may not work.

Lime: The best thing to do is get a soil test, but failing that, ask the county agent and/or nearby neighbors how much lime is required in the local ponds. Generally that is a fairly safe way, short of a soil sample, although variations can happen within short distances. If you need lime, now is the best time to do it, before the pond fills.