Are you sure what you got from the hatchery? It is not unheard of to get a GSF or 2 in some BG deliveries. Over time in a BG/LMB pond it should work out ok as per Bruce and Dave's comments. I hope you got a chance to look over the BG before they went in and there are only a few GSF. If they brought you HBG with a few GSF that is a different matter .