I have a similar problem, I bought some type of material like a pool noodle (used to insulate the a/c tubing) from the hard ware store (I saw they also have something used for filling cracks, its grey on a roll, again same pool noodle feel to it - but very thin like 1/4 inch pool noodle), anyways, I bought the stuff, cut it into long strips and just corralled a bunch of floating plants in front of my problem area (I used water hyacinth). I used rocks to anchor the edges so they will stay in place. Of course the fish started eating the roots, so I found some very light netting and just sewed the net to these grey 'pool noodles' and so far its working great. The baby fish get in there, but the large ones can't eat the roots.
I was trying to find the product on Amazon to attach the picture, my description sounds a bit weird. If you're interested I can take a picture next time I'm at the hardware store.
Its nice because you can make it as long as you want to hide the problem.
Priscilla