Sphagnum is the latin name of the most important genus of peat-building mosses in the northern European and American bogs. Stefanie obviously did not think of peat but of living plants that grow in peat ditches and built our peat over thousands of years.
It’s good an idea since Sphagnum needs very acid environments with rather low pH similar to those in the homelands of our fish. The only problem I see is temperature. I do not know whether Sphagnum tolerates higher temperatures. I tolerates very low temperatures since it exists in the north of Norway and equally in northern Canada. Unfortunately I do not know what it’s southern border is. There might be a need for high concentrations of oxygen bound to those low temperatures, but that should be tested. Another problem could be light. Living Sphagnum needs much light. It is constantly growing at the uppermost end, the surface of the wet peat, and it immediately dies to peat if overgrown by itself. In the case of dying it lacks light and it does not need it any longer, but living it needs a great amount of it. One must try.
We do use some European plants in or near the water in tropical aquaria that normally do not live in countries with higher temperatures, for instance Lysimachia nummularia or Hottonia palustris. Maybe our Sphagnum stands it, maybe not. But equally other Sphagnum species may exist in the homelands of our fish, too, participating on the peat building processes over there. Is there anybody here who knows? It would be not astonishing that the aquarium trade has not discovered them as Aquarium plants for they would be useless for the standard aquariums and without use commercially. They really need very low pH, do not only stand it.
Well, one should have a try. But you may not remove those plants from Nature reserves; it’s rightly forbidden. Try to find a region where this is possible without harming the biotope.