I have a flame and koran in a 75g f/o without live rocks and they are thriving and healthy. Both are eating, pecking on the algae, and swimming through caves. When you put the fish in, make sure it is dark and try re-arranging the rocks to confuse the fish. It should be O.K. My problem was with my sailfin tang. It attacked the Koran the first couple of days, but now they're like best friends.