If you just want to temporarily cut them back, do just that. Cut the stalks off (I use a razorblade that I dispose of afterwards), and yank 'em out.
I almost wish I hadn't got xenia -- they're such a pain. I'm trying to rid my tank of the brown variety, but if you don't scrape every last bit off the rock, they'll be back in no time. And they stink. Badly. I can't eat mandarin oranges anymore -- my fiance agrees, they taste just like the xenia smell. (BTW, he knows this because I make HIM weed the xenia out..hee hee...)