People have successfully fed harlequins chocolate chip stars for a long time. They have fed them arms. They have fed them frozen bits. They have had no problems.
The most ecologically friendly stars to feed these guys are the small Asterina stars that people have...they reproduce readily in a refugium or sump, and people are always trying to get rid of them. If money is your only concern, then that is the cheapest road :roll:
The next friendliest thing to do is to keep chocolate chips in a refugium or sump, and cut off arms. Harsh, but true. Feed the stars so they can regenerate the arms. Again, a cheap option. This will not work with delicate stars like Linckia.
The next best thing is freezing the stars, and feeding the arms. This makes the best use of one star.
The least ecologically friendly thing to do is feed stars whose wild populations are highly pressured because of this, and other hobbies, this includes Linckia. Apart from the dismal survival record in this hobby, take a look in any shell shop or craft store and see how many Linckia you can spot. Multiply that by every shell shop in every smarmy beach town in the US...and the world.
There are plenty of animals in our tanks that do not get exactly what they eat in the wild. There are plenty of animals sharing close space that do not live within thousands of miles of one another. Please don't use the argument that they need Linckia stars because that is their natural diet. Doesn't stop us with most other things. They clearly eat other species of stars, and some other species (Asterina in particular) are more responsible (and cheaper) choices.
However, I am quite opposed to keeping something with such a specialized diet simply because they are pretty :roll: But we all have choices.
I am not opposed to animals that eat other animals, and am tired of that argument with respect to harlequins. Just spend some time thinking about the different options in what to feed them. Some options are more responsible than others. We all have choices.