Bifferwine
I am a girl
Unfortunately taking the starfish back isn't an option since I bought it online and the guarantee period is over. Do you think a serpent star would be OK in the same tank as the sand sifter or will they kill each other? Any type of serpent in particular?
They will be fine together. But the sand sifting star is going to starve to death very quickly. So you should take it back to a store. You don't have to take it back to where you got it from. Any store will accept livestock.