Glossostigma elatinoides occurs naturally here in Australia in a variety of habitats, especially in perennial swamps in the high country. It tends to be marginal and extending well into submersed areas of the location. Although it seems to prefer a muddy substrate it is often found spreading around and between rocks in shallow running water. In my experience it requires a high light intensity and limited temperature. I grow it best outside in shallow trays (1-2" of worm castings covered with 1/2" of sand) with only an inch of water over it and full sun for a couple of hours each day.
I have a friend who grows it quite successfully in the aquarium situation and it was very slow to spread until he added CO2 and it has done well since. I suspect this species is sensitive to prolonged temperatures above 26C so it would not do for a Discus tank.
There seems to be another species that I have seen in nature growing in shallow flowing water in the Koolatong River in Arnhem Land. This form has much broader leaves and is a deeper green in colour.