arond,
A long time ago I grew on the shores of Lake Superior in Northern Wisconsin. The regional landfill was on the lake shore just outside of town. I also spent six years in Uncle Sam's Navy. I've spent way too much time watching seagulls. I don't know a whole lot about them, but I'm not sure there is much they won't eat -- dead or alive.
Just a note -- seagulls are federally protected. Most states and municipalities also protect them.
Although they could have eaten all your FHMs, I figure the minnows got smart. They probably quickly head for cover and deep water at the sight of any shadows.
I know they are difficult to control when they decide to invade. Google "Seagull Deterrents." There are a lot of suggestions. I can't vouch for any of them.
Sorry I haven't been much help. Hopefully, one of our other members has some suggestions on how to keep the crazy white birds away from your pond.
Good luck, and keep us informed. Tell us a little more about your pond and plans.
Ken
