I have used, and continue to use, both the fishing line and the drip tube hoops. If you have a koi that thinks hyacinth roots are something to snack on throughout the day (like mine) you can add a basket to the bottom of the hoops constructed out of any type of plastic coarse mesh or “deer fencing”. This is put together with wire ties and attached to the hoops with same.
This keeps the koi away from most of the roots and provides a place for the smaller fish to hide. If you want a floating island, simply attach a piece of fishing line to the hoop and a non-corrosive weight of some type. This will keep it in the middle of the pond even with a current.
I modify the hoop-and-basket idea and make them any shape I want and tie them fast to rocks along the edge of the pond.