I would take it back to your local LFS, tell them its not compatible with your tankmates. If your lucky you might be able to make a trade with your LFS for something within the price range of the crab. I've done that before. Good Luck...
Thanks for the advice everyone, and when I bought the tang they said it would do perfect in a 12 Gallon tank and thats why I bough it. I will definitely not go to that store anymore.:shock:
12 Gallon Tank but Salt and pH are all good.
They are florescent white and blue lights.
I have 2 Blue Damsels, 2 Clowns, Royal Gramma Basset, Blue Hippo Tang.