I completely feel your pain. As of now my tank is slowly being taken over by this invasive macro algae which people on this board have so kindly identified as a kind of Kelp. I've tried everything too, including reduced photo-periods, overstocking a cleanup crew, Removing all the rock and keeping it in the dark for a month, buying 3 Sea Hares. Nothing seems to work, this algae just keeps coming back.
I totally understand why you went so extreme to rid yourself of your algae problem. I think I'll try what you did, but I have a much smaller tank (30 gal) so hopefully it won't be as hard emptying it out. Your tank is coming along nicely, I hope my attempt will be as successful as yours.