Java moss seems to be the easiest for me. At first mine seemed to melt but then it took off after a while.
+1 having co2 is beneficial but not required.All moss does well without co2
Nope even mini pellia don't need CO2 but like all moss they will grow faster with CO2 and fertilizer. It seem that most moss prefer cooler water then tropical tank. I found java moss indestructible even at temperature over 80+ and my goldfish leave them alone.I think one of the only mosses I've heard "needing" CO2 is mini pellia. Not so sure about that, though.