One of my many small BTAs got sucked against a Nanostream intake. Wasn't torn apart, but received the same level of damage any other pump intake would have inflicted. It has since recovered, always amazed at how much damage those guys can take. Anemones will wander, and they will get sucked into any pump intake that isn't protected. While it did not get sucked into the pump, suction is good enough to keep it tightly pressed against the nanostream. I'll take my chances with the exposed nanostream. If I see an anemone on the move, I'll simply turn the pump off for a few days. You can try keeping the nanostream in an upper corner of your tank, far away from any rock outcroppings. Also, you might want to think about re-arranging your rock into an "island" if you are keeping anemones. I've found that BTAs and others will not care to trek across the sand to make their way to glass. While it won't stop them from moving, it does keep them from wandering up and down the walls, which is usually the most dangerous place.
jb