HC, UG, Dwarf Hairgrass, Glosso are all good candidates.
You may need to spray the plants on the "hill" on a daily basis to keep them moist enough. I don't think there will be enough water otherwise.K, the bottome of the tank is in the emmersed state. The hill is transformed. Would be ok to start putting plants on the hill? Is there enough moisture going up through the substrate? The hill is basicly flora max.