Sphagnum moss growing?

[james j]

I have a some random moss growing around my terrarium, some of them get a little out of control so I pluck it out occasionally.
I noticed this odd looking patch taking over one of my plants so I plucked some out. I thought it was moss growing on some sphagnum I packed around a plant. On closer examination it looks like the sphagnum itself started growing.
Is that what it is, I’ve never seen live sphagnum before? My first thought was “cool I can grow my own sphagnum “ but is it a good thing? Will it take over the tank?

Thanks