I would suggest Water Wisteria and sword plants. I have both in my tank with arowanas. they seem to fare pretty well. i spend a lot of time replanting the water wisteria as my aros get spooked easily and tend to jump and uproot them. they are pretty hardy and fast growing though so i imagine they uptake a lot of waste from the tank. with sword plants i find that their roots grow deep once they are established and are not likely to be uprooted by the aros.
btw, whats the second fish in there, is that a peacock bass?