It could be java or christmas moss. IME, with a low tech set up, the difference between the two types is barely noticeable but with more light and nutrients or CO2, the Christmas moss looks darker and thicker than java moss. Of coarse you would need both to do a comparison. Moss looks really different in each person's tank. If you are looking for a moss that you can tell what it is in any lighting, try flame or weeping moss. The growth patterns of both are unmistakeable. They don't attach though, but do look very nice depending on where you use them.