I find it funny that there are two opposite sides to this "do they don't they" eat zoas business.
When reality is there are so many different stars that one cannot possibly identify them all or possibly know exactly what their diet can consist of.
We had seen these stars on a zoanthid colony of ours. A very rapid growing colony.. they started to diminish, not all the zoas in tank, just those on that one rock. 3 seperate types of zoanthids. No distress was visible, tank parameters were in check. The ONLY change that occurred to stop them from disappearing in our tank was the addition of 2 harleys.
So the logical explanation in my mind, considering I have not changed a thing about my tank maintenance routine itself, is that the Harley's eliminating the stars is why my zoas are now again growing rapidly with zero decline.
Did the stars actually eat the zoas? I don't know for sure.. though they did have an effect on the zoanthids, either due to the stress of their presence alone or actually eating them.