Seeing HC work in a DSM NPT is encouraging; to me it signals a very big advance in the hobby. I've found my HC growing phenomenally better with DSM, but I haven't tried it without CO2 post-fill. The roots are vastly longer, there's no melt on introduction, and it seems to change growth patters within a matter of days.
Perhaps getting it established is more the issue than having enough CO2 long-term. Adding tons of CO2 would definitely help the stuff to root/grow better in a traditional planting method, and getting good distribution to the bottom of a tank at those levels would require compressed CO2. When people use compressed CO2, they tend to push their light levels higher which would also contribute to it. Even then, HC is a pain to plant and establish in a filled tank compared to most species.
It may be that increased CO2 triggers rooting as well. I've noticed that plants on the high CO2 demand list are usually found in rivers, they're smaller, and they tend to grow near the water line. Getting caught along the side of the river bank, especially during low flow rates, would be a natural time for them to successfully establish roots.
Maybe it's some of both; the two concepts aren't mutually exclusive either.
Then again maybe it's neither and I've missed the point completely.
Either way, I think observing what happens over the next few months to year will say a lot. I'm wondering if the generally mulmy bottoms of an NPT are the sort of thing HC will do well with. There may need to be some adaptations as NPT tends to recreate more of a lake than a stream.
The plus side with all of this is that HC is very easy to grow emersed. Emersed growth trays are also incredibly cheap and easy to maintain. You can grow a big mat of HC from plugs inside a few months with minimal care. I think HC is something that everyone should try out if it's making it through DSM and no CO2.
Either way, nice work Diana. I'll be very happy if HC can be separated from compressed CO2.