Can't seine then you catch them goldfish whenever you can. Just a baitfish that outgrew it's reason to be alive. If you notice most all the guys go with minnows, fatheads, gambusia, threadfin and shiners. They rarely if ever outgrow their use as forage. I would have held off on the new bg, but it's your pond, you do what you want. Goldfish can be so invasive some states even outlaw them as bait. Sounds like you enjoy the pond and the kids do as well, can't argue with that. I'm really surprised you don't have a lot of little ones, they are prolific breeders and lay eggs everywhere.