Most Hoyas as I have found this year root exceptionally well in moist coconut husk, but what happens after that? This is the question that I keep working on. You have to be really careful with coco husk as much of it is very salty as some of it sits in ocean water for months before it is processed. It is always safer to soak and rinse many times before using it. I have many plants currently rooted in it, but while the roots can be amazing, I seem to have a lot of trouble to get any new growth above the soil line. At this point I can’t really recommend this medium as it is also very easy to rot the roots with it.