Yeah, some people believe that the "Asterinas" (technically Aquilonastras) the Linckias eat allow their stars to survive in their tanks - I've suggested people may want to try farming them to feed their Linckias as a result. They likely do also eat tunicates and sponges, as those tend to be bacterial sinks (so they'd basically replicate biofilm for the stars to feed on).Multiflora seem to be starfish & tunicate eaters in my experience, mine eat 3-5 asterinas per day and I've seen them parked on some colonial tunicates that have made their way into my tanks. All of them are regrowing limbs from fissions before I bought them, so I'm hopeful they'll continue to propagate in my own system.
Genuinely glad to hear they're doing well for you - please keep us updated on how it goes, as most of the time I've heard these stars typically die off around ~8-13 months in our tanks (though I've heard of them making it to ~2-3 years if there are Aquilonastra stars in the tanks with them - they seem to basically wipe the Aquilonastra population out after/around that time).