I've breed GBR for years now. For me, most GBR pairs are terrible parents. They will get to 2 or 3 days free swimming and then they will eat them. They are easy to raise without the parents and I find this is the best way go. Place a 4" terra cotta saucer upside down in the tank. I have found they will always lay eggs on these if they are present. Once they lay eggs simply pull the saucer and put it in a container of your choice. I have used the plastic shoe boxes. I like to place some java moss in with the eggs. Then change water a couple of times a day. They will eat bbs. If tank space isn't a problem, my preference is to just pull the parents from the tank. I use 20 gallon tanks for my GBR but even a 10 would do. Like discus, once they start laying eggs they will continue regularly.