Theo, I don't have any artificial structures in the pond at this time, so that shouldn't be a problem if I do end up adding CC at some time.

I do have a 4" bottom withdrawal siphon spillway. Do you think CC would try to spawn in that (and then get sucked out once the overflow kicked in)? The inlet end of the 4" pipe has a 2" reducer and about 10 2" holes drilled through the top of the last 10' section.