Aquarium moss
Fontinalis, Christmas tree moss, Java moss
I need to get some more photos of mosses, but below is the three I have. I believe the first is what's being called Christmas tree moss, the second is Fontinalis antipyretica, and the third is Java moss, Vesicularia dubyana
Christmas tree moss
This is a very pretty moss. It tends to stay lower though will eventually grow to large mounds of moss. The moss in the photo is growing up the side of the tank. This moss is called Christmas tree because the stalks branch out in a pattern similar to the shape of a Christmas tree.
Fontinalis antipyretica
Fontinalis is an old time favorite for the aquarium. Fontinalis has larger phyllidia (leaf like structures) than Java moss and they are more pointed than Christmas tree moss.
Vesicularia dubyana
Java Moss
This is a lovely moss that will creep over an entire aquarium. In fact it can get to the point where it smothers everything else in the aquarium if it's not trimmed somewhat regularly. This is another good plant for breeding egg laying fish.
For more information about aquarium moss please see my March 2006 column for TFH's "The Planted Tank," called Mosses.