Here's my tank with over 30 of them playing nice... most of the time.
There's a BTA mountain in the back left corner and a magnifica on the right.
Plan the position of the anemones island taking into account where the flow will take them if they take off. In my case I placed them right below a pump. I prefer that they meet the pump than landing where they shouldn't.
That's interesting. What pump do you have above them? I've always been afraid of nems getting sucked into powerheads (happened once) because I heard they will kill everything in the tank if you don't catch it right away so I placed powerheads far away. That's possibly what is pushing them to walk since they get stronger flow than they like..