Good Fish or Bad Fish

good star or bad star

 

asterina - I think some can aggravate coral but mostly harmless - can multiply and become a nuisance so "in between" bad and good

 

It's one of those watch and wait scenarios, there are hundreds of different types, most algae eaters (including coralline), some prefer zoanthids, some actually sps corals, then you add the opportunistic eaters.

If you see the star on the glass grazing then it's probably a film eating variety, if the star in hanging around zoanthids then he is probably also dinning on zoanthids.

One type of asexual reproduction is lateral fission, leaving a leg behind witch regenerates into a new individual. If you see this type of display frequently it's probably best to start to manually remove them as a means of population control.

 

I'd just start removing them now while the numbers are smaller. A lot easier than waiting till you have millions of them in 6 months IMO