Xenia doesnt always spawn by releasing gametes into the water. What it will do more frequently is to grow nodules on the sides of it, lean over, attach those nodules as polyps to the rock next to it, and stand back up. They basically spread like weeds.
"Smoking" is typically a spawning event. Although uncommon, its not unheard of. And ironically spawning events are usually a sign of a healthy tank![]()