On porous materials like lava rocks, the super glue tends to get absorbed into the rock. If disturbed too much before it dries, it becomes crystalized opaque and not transparent. It is a pain, but separate the moss into single strands then place on rock and place a drop on top. Let it dry out of the water for half hour, it will not harm the moss. A better glue on porous rock is epoxy. Place a drop on the rock, it will not be absorbed into the rock, and put a strand of moss on the drop. If the drop is not disturbed too much it will dry clear. The working time with the epoxy is longer than the super glue.