So far my octo has cohabited perfectly with 3 brittle stars, a sand sifting star, a Fromia sp. star, and three urchins (two blue tuxedo urchins and a pencil urchin.)
I have heard that they don't interact with cucumbers, either. But I have heard so many horror stories about cukes that, although I really want one, I'm terrified to get one. They can release lethal toxins into a tank (especially the pretty sea apples that I want), especially upon death, which seem to especially kill fish, and MAY not be a threat to inverts. They can vomit/eject their internal organs or Cuvier tubules (I think I remember that name properly) in defense...which can again toxify the tank, but worse, the tubules are incredibly sticky, like glue. A fish covered in them isn't likely to survive, plus it's nightmarish stuff to try to remove from the tank.
Colin...any experience on that? Would a sea apple dying in the tank harm corals/other inverts/octos?
rusty