I have an asterina starfish outbreak. I added a harlequin crab to my tank Saturday. He's moving about a bit, but the starfish seem to have multiplied rather than been depleted. I read they eat up to 15 per day. When should I see him begin to eat, or are they nocturnal? Also after I scrape them from the glass, do i need to siphon them up, or can they stay in the sand? Thanks in advance!