Question Need an ID on a starfish

[Pagodazoa]

I have two starfish in a 12 gallon nano. One was sold as a “mottled” starfish the other as an orange linkia. I added a smaller red fromia which the mottled star ate. Is it due to the size of the star I added or because it’s from a different family of starfish? I’m trying to add a tile starfish around the same size but reconsidering it to avoid adding a fromia family star. So far these two have gotten along well, I feed them a clam on a half shell each twice a week