Well, these lyretails seem to be nibbling the green leaves off the moss... Saw my lyretail reducing one whip of the moss to a stick.Typical common livebearers will pick at plants and any other surface almost constantly. For a plant person, the action means nothing. The livebearers are after the micro-organisms that normally live on plants and other surfaces. They do not "eat" plants at all but will not hesitate to eat dead plant matter or similar non-plant materials.
My ramshorns are mostly on the glass / filter though and I see my lyretails taking off leaves in their mouth. My apple snails, however, eat the whole whip like it's spaghetti.I always thought it was my platys destroying my plants as they were always picking at them, but it seems they were just nibbling bits of algae etc off the leaves, it was nasty little pond snails doing all the destroying.
Since I put a few assassin snails in, I have noticed a significant increase in my plants health.