I'm all for the 2 pond idea. The top one would collect most of the runoff/nutrients, so make that the fishing pond and use the downstream one as the swimming pond.

Having two separate fisheries that close to each other is a lot of fun. When you get tired of one or the fish aren't biting you can switch to the other. With two ponds in series like that keep in mind whatever fish are in the upstream pond will likely make it into the other.

Every person should have an interest in life - I think I'll go fishing. ~ Thoreau