I would use them in the pond as structure. Stack them in such a manner as to have as many gaps as possible for water to flow in and around. Make the structure have some height because anything laying on the pond bottom will eventually be covered in silt. So something 6" high in the pond bottom will eventually become 0" high and be useless. Whatever you make as structure, make it at least a few feet high.

I have used flat concrete chunks where I know water will be entering the pond and dropping off a ledge. You can dig in the flat chunks and make the water run over the concrete so the soil will not wash out in that particular area. Keep in mind what Esshup said about mowing though. If I can find pics of what I did will post them.

John

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