The big cage discussion from '08.
http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=170120&page=3

Looks like you need smaller mesh of 1/4-3/8".. see pages 2 & 3.
Also old PB mag issues.. apparently there was a series.

I stocked ~3" LMB, and some of those could get thru 1/2" mesh I'd think.