I don't know. They say sometimes you can get them to split if you want to by stressing them. One theory says if you feed them really good and then do a water change that can trigger a split. But I've also heard that there are just some that split and some that just don't.
I've done plenty to stress mine I'm sure, but it just must be one of those that never splits. When I first got it, it kept trying to crawl up and use the teeth on the over flow to split. One piece did come off, went into the overflow and made anemone soup in the skimmer pump. I came home to find my whole tank milky white and smelling of anemone.
Maybe that traumatized it into never splitting again. :rollface:
JK of course ... don't think anemones suffer from childhood trauma.
I was looking back at pictures of my tank. The anemone started in the lower right section of my rocks and stayed there for a few months. I remember when it went on the move .... all of the corals in its path looked like they'd been napalmed. He worked his way to the highest point in the tank with the most flow somewhere in the summer of 2004 and hasn't moved since.