Overflow cover?

So my new tank has an overflow.

Is there a something i can put over the overflow to prevent my bichir from swimming into it? (hes about 3.5" long)

would this same cover be effective in preventing duckweed from clogging my overflow?

Dont think that there is really anything.

i dunno if it would work but it brings to mind how some people use plastic canvas to cover portions of tanks they don't want fish to jump through...