Right off the top of my head I would put 2 posts at each end of the spillway and say 1 every 4 foot just like a 2x2 post say 3 feet long put it in the ground about 12 inches then run my mesh or screen all the way across and down in the pond. I would use something a little stiffer than mesh. Say 1/4 or 1/2 inch chicken wire. It's only 20 feet so it wont cost much to replace it every 2 years if need be. Then staple gun the wire to the posts you bigger fish can swim away from it they just like to go with the current as soon as they hit the screen they will go the other way. You smaller fish may lay up against it some but that's better than being out in the field... lol
Good Luck
RC
