I've used a syringe to kill majano anemones and injected them with calcium.
Worked wonders and never have returned.

But the best and natural way to control aiptasia was peppermint shrimp.
Mine have died I'm guessing 'cause I haven't seen any and my aiptasia is beginning to return.
My local stores haven't been carrying peppermint shrimp. :( :(
And I'm sad that I haven't and won't be able to visit S.A. because I'm short on cash and my bf now works Saturdays.