Drago your mesh bag sounds like a winner and an easy solution. Did you just tie it on the pipe or use Velcro? I overthink things and was contemplating having an accessible clean out where I could put in some filter material, this was mostly for if used my shingled roof.

Fish are ungrateful and will try to swim away 😉, before my overflow was installed they would escape my pond onto the lawn where the pond overflowed.

[Linked Image from i108.photobucket.com]