Welcome to the boards.
I just read through your other post. It seems that you are very new to the hobby. Yes, starfish and anemones can coexist together in the same tank. There is a little more to think about that what the BTA might eat. They need established/mature tanks with stable parameters and good lighting in order to thrive. New tanks don't offer most of that.
How long have you had this tank?
What do you have for lighting?
What do you use to test?
Can you post everything in the tank (inhabitants, equipment)?
How often do you do water changes?
What salt are you using?
Do you use RODI water?