The ONLY way that you can be certain that no anemones will be damaged by power heads is to not have any in their tank! It is simple to use a large return pump in the sump for their tank! You asked "what will keep them alive, and happy?" Hoping that stable parameters will do that is leaving things up to chance! Having nothing for them to get tangled in WILL give them 100% of a chance to live!
They all deflate after they eat, so that means if they eat, they inflate, and deflate for their whole lives, not just months. None of mine died, ever, until in same tank with the nematocysts of killer green anemones.
And if you would like to try mixing anemones the way that I did, start with 20 very healthy rainbows, and add a green kryptonite to the same tank. They are fluorescent green with an orange dot on the tip of each tentacle. Let us know how it goes!
