A few days ago ,
I'm watching some people's Live show ,
then ,that player found the bug of fish ,
that me describe the method :
1. make a pool
2. put a "stair" in water
3. use the "fish bucket" to click the stair
then done ,you copy the fish .
i'll put the "address that Live show on Youtube" to that everyone watch ,start from 3 minute .
PS. :Because i didn't actually test ,
so i don't no whether any of "stair" or "fish bucket" can do this or not .