It is rare to have a problematic asterina, and we don't even know that is what the OP has!
Most people are not even aware they have these stars. I have never heard them reaching population levels where they smother corals. Higher populations in most cases are due to high nutrient loads and this will kill corals too. Like many cases, the star is blamed for nothing.
I strongly discourage removal unless you have reason to believe there is a problem. And in most cases, the overwhelming majority of cases, they are not an issue at all. Microbrittlestars are highly desirable if that is what you have.
Species of Asterina are impossible to differentiate even by seastar experts. Arm number, color and size are not accurate features to use. If they are wandering around on glass or hard surfaces the odds of them being predatory is very low. they do not become predatory, but will consume dying corals.
IMO, absolutely leave them until there is a real issue...which in most cases will be never. even if you have coral issues, odds of it being these stars is very low. THere are predatory one's now and then, but this is quite rare. Not impossible, but absolutely positively not worth removing "just because."
If they have really thin arms, sticking out of rocks, they are brittlestars.
I am very much opposed to hype in this hobby. If we removed or eliminated everything that "might" be problematic (eat, kill, overgrow corals...), you should never introduce live rock, live sand, frags, live foods, crabs (of any sort), shrimp, bristleworms, amphipods, urchins, brittlestars, seastars, many types of fish, many types of encrusting corals or any that may grow for that matter, sponges, etc.....in short, you can take the joy right out with it.