This invasive flatworm can be found in gardens etc in a couple of places in Europe already. It's natural range is in Australia.
It's an Isopod feeding species and can be quite ferocious. They secrete a very sticky slime with which they catch their prey. It also seems to dissolve the prey, so it can feed from it. Only that will be left of it is an empty exoskeleton.
As an enclosure I use a tight sealing plastic box. For substrate I use some moist peat, I also add a piece of cork and some sphagnum moss. If it's suitable for isopods, its suitable for the flatworm.
Breeding them is easy. Just cut them in pieces. In 2 weeks they have regrown their missing parts.
Sexual reproduction is possible, but I haven't witnessed it yet.