I know plenty of people that have had these stars in their tanks without problem for many years. The reports on the GARF website regarding the taste of their sea stars for certain SPS are pretty dire, however, so it's worthwhile keeping an eye on them to make sure that you don't have a problem with them. Again, although these stars are opportunistic carnivores, my guess is that problems with them in the tank are a result of size, population density, and feeding regime of the tank in question. I would say that in general, people who have relatively few of these stars, or have only the stars of the small variety (never get more than 1/2"), almost always report "they don't seem to cause any visible problems in my tank..."
If you find that they grow larger than 1/4 to 1/2" or you are convinced that these stars are the source the problem with your Tubipora (as opposed to cleaning up a slowly failing colony), though, there have been successful reports of using the Harlequin Shrimp to remove these cryptic stars (e.g., also on the GARF site
http://www.garf.org/news28p1.html#star). If you're really set on removing these sea stars from your tank, that is probably the best way to go, because these stars are primarily nocturnal and so cryptic that you're almost guaranteed to miss some in any manual removal attempt. The Harlequin Shrimp will do a much better job than you will in finding all the sea stars in your tank if you're determined to remove them, but when sea stars become scarce in your tank, you'll need to start buying small sea stars to feed the shrimp, because I have never heard of one being kept alive for any length of time without sea stars on which to feed....
