Here, have an update:
I'm trying to grow H. tripartita emersed on that sponge. Hope it fills in pretty quickly. As you can see the wall was not going so well. I transferred the moss to rocks to make sort of a carpet.
I've had the worst luck with any and every type of plant except H. tripartita, so I'm trying my hand at crypts to see how it goes.
All of my shrimp have died, but their babies are almost full grown. I'm going to replenish the colony soon with some cherries.