thats a pretty barren looking scape to me. You dont need to go crazy with rock. IMO the less rock you have the better its gotta look, because all of that openess will be really the first thing they see, how much sand are you going to put in ?
I agree....unfortunately I think you need at least double that amount of rock....or at least combine it all and form one structure (since you are only adding one pair of fish anyways).