The only advice I have for you on GBR breeding is that I notice the females stomach goes red when she's spawning, the male chases the female around my tank for about 3 weeks but when her stomach turns reddish, she tends to slow down a bit and looks like she is giving in to the male. They rub against each other now and again and normally after that you see her stomach getting fatter. When her stomach is red and she's ready then her fins stand up and the males colouring also gets more vibrant. When the female is ready to give birth, she moves to her chosen spot, her tail fin flutters and before you know it there are about 30 eggs there, the male then takes over, fanning the eggs for a minute or so and the female retakes her position and lays another 30 or so eggs, this happens between 3 and 5 times before the female swims off and leaves the male to do his job. He fans the eggs and guards them from anything that comes near. The 2nd and 3rd day, both parents take it in turn to guard the eggs. That's all I know about GBR breeding as that's as far as I've got with them. Hope I've helped?
) and placed several pieces of med to med/lg pieces of flat rock (like cobblestone or shale) for them to spawn on (nothing real big). The key I found was that they needed privacy and acidic water to spawn even tho the fish had been acclimated to alkeline water to be able to sell to the stores. I also took the spawns and artificially hatched them to reduce the chances of the parents eating the eggs. ( Dealer's choice on this as some are good parents.) Breeding temp was 78-80 degrees. Lighting was on a timer for consistancy. I also had some cave like areas in the tank for more security. 
