jonathanw,
Welcome to TR.
Q1. I doubt that many of your sand critters will make it over to your new tank. The exception might be the larval stage of some critters may be swept into the current and make it over. You can help it along by transferring a few scoops of sand from #1 to #2. I understand your concern about the
cyano but, that has probably already invaded #2.
Q2. I may be wrong but, I doubt your starfish will eat the Star Polyps. There normal diet is shellfish in the form of clams and such. I have fed starfish small pieces of fresh raw shrimp. I would cut a small piece of shrimp and place it under the starfish. It was especially interesting to do this while the Starfish was on the glass wall of the tank. A starfish eats by inverting it's stomach surrounding the shrimp meat and dissolving it.
If you can, post some pics of your systems. We love pics.
Dick
