Hi there, any kind advice on choice of plants to achieve this kind of look.
Possible to be done emerged in humid conditions initially?
Attempted with Hydrocotyle tripartita Japan but didn't work out.
I've seen it done with a lot of different things, mosses primarily, as @minorhero said, moss balls are common, but I don't see why something like java moss, Christmas moss, etc. couldn't be used. I would think about the flow of your water, as you don't want your bonsai tree to include an array of fish droppings and uneaten fish food, and other debris, maybe position the tree in a spot in your tank where flow is quite high(by powerhead, filter output, etc.) Have fun!