The floating plants can be anchored. Hyacinth & lettuce can be kept in a "hula hoop' type thing that you can make out of black tubing. Then anchor it where you want it with fishing line.
You could probably do that with smaller plants, too. Like Duckweed & Salvinia.
Sometimes, the fish figure out how to swim out. I usually check once a week or so, and net the fish out.
I get a lot of submerged plants in the skimmer, like anacharis. I just toss it back into the pond. It's probably the same piece over & over that I keep tossing back.
