I never thought about the ponds above me when I built mine. It has been dry here for sometime and not much heavy rains but this year my spillway was used several times. Now have those unwanted fish. I though about just getting me some D&B Catfish and just let them eat everything up the take them out and try again but it would just happen again. Just not sure what I need to do. Just deal with it or give up and start over.