It's wanting to move, if you have a small frag of live rock' you can lay it near it will crawl and separate from the main
stalk from its parent colony, meaning it wants to "split" in two,
( this is how they move they will actuly let loose of the rock and tend to move in the direction of water flow.)
It wants to make two for you , lay a rock near the piece thats separating and watch !
As well xenia can handle some nitrates and they do tend to do better in tanks that are fed more than less.
( xenia do poorly in a nitrate/phosphate absent tank , and they LOVE light the more the better it seems )
Now im not saying xenia can handle HIGH nitrate levels , but they do very well in a tank that has some in it.
LoL , turn your power head back on .

how many ya want ?.lol