I can confirm that Java moss is easy. I only have 20w light on 25g tank. My CO2 level is very low according to my KH/pH levels. Despite this, it seems to grow well, showing light green branches growing everywhere...
As for Java fern, I have a question. I bought it at the same time as the moss (about a month ago), and as I read, it seems to grow ok under low light condition. Lots of new root/leaves that form at the end of mature leaves. How long should the mature leaves be? I was under the impression that they could go up to like 10 inches. So far, the longest leaf I have is about 3 inches max... Did I get a "dwarf java fern" is such a thing exist?