My water hyacinth just floats free. I don't have a water poppy so I can't speak about that plant.

Anne

If you're worried about the hyacinth floating into the skimmer, I have used fishing line to hold them back. I've also seen people use hoola-hoops, but it will probably need to be tied to a rock to keep the whole thing away from the skimmer.

That planter is not appropriate for either plant.

Hyacinths float free and water poppies are planted below the water surface like waterlilies.

That planter would be great for aquatic forget me nots, water celery or parrot's feather though....