It may not even eat the asterina.

 

How big of a tank and where does the brittle star "hang out". If it is in a convient place to catch him, just use a piece of krill or seafood big enough to hold between your fingers. If you can reach the brittle star with this bait, it will be hard for him to resist going after it and he will likely wrap around your fingers to get the bait. Then you can kind of gently move him out away from the rock and just pull him out. I finger feed mine a lot, especially when i want to freak out company!

Arrow crabs also eat asterina stars but can be damaging to other stuff as well.

 

believe it or not he is just in my 29g nano cube but i have 40-45 lbs of rock and they are covered in coral and he is under the main middle rock. since the first day i got him he is super wierd. Ive had him for a year and after the first month he just stays under that rock and sticks his arms out. when i feed the tank he will grab food and pull it under there but he never moves from under there. Ive checked at all hours of the night and during the day and he wont come out. i tried to get him once but ended up just taking off one of his arms but since then has grown back. The only reason i dont like him is that he is always grabbing at the fish when they swim by but i guess not super agressively. The asterina stars are everywhere and i can see where they have been eating my coraline.

 

I also wanted to get a goby which i think unless i get a big one he will probably just eat it. I got a yellow watchman about 10 days ago. he was super small. he went under that rock to hide in the first 5 minutes i had him and then i havent seen him since. I hope he is just hiding out in the rock but i doubt it.

 

The brittle star just reaches out blindly, trying to touch food. It won't hurt your fish. It'll never be able to grab on to a fish, unless the fish is dead or dying.

 

Is the brittle star green? Only asking because i have heard the green ones can and will eat fish. Maybe you can bait him out of the rock at night when they feel more safe. I doubt if the standard trap will work. Good luck.

 

no its a black one. yeah maybe I will try at night. I still have to catch a scat thats in my tank also. Its hard getting things out sometime thanks