Ditto what Dave Davidson said. I don't think the HSB will be able to keep the CNBG offspring in check.
For a 1/4 acre pond, HSB will control over-population of CNBG very effectively with the assistance of one female LMB....if pond is free of structure and cover.
One grass carp and same sex tilapia worked well for me.
Small ponds are fun!
G/
