Originally Posted by Nachos
miremonster, I think that link you posted is the same stuff.
I think it might
be the same, but there are many creeping moss species from different genera and even families looking like this. It looks to me like several mosses occurring also in Germany, and if it would grow here, from the pic I couldn't say for sure if it's e.g. a Brachythecium or Hypnum or Homalothecium species etc.
Heck why not, I'm gonna give it a shot submersed and see.....
Many terrestrial mosses may survive or even grow submersed, the better the conditions (light, CO2, rather low temperature,...), the longer, but it may be that the submerged shoots don't look well (e.g. Climacium japonicum), and I agree that Your moss from the tree is likely not suited. But it's also good to show what happens with the moss when drowned in a tank.
I'd recommend to look for mosses in damp places along water, in swamps etc.