With a perpetually hungry perch in my pond, the only way goldfish fry could survive is to escape while they are tiny via the skimmer and risk the spinning rotors of the pump and manage to get through the tangle of netting I use for bio-filter and into the small top pond that is free of any larger, hungry fish. And that's exactly what a couple little fry managed to do the summer before last, but I didn't notice them until early this spring when I decided to revamp the waterfall which required draining the upper pond of all water and removing any living thing.
Besides the two little 1/2 " goldfish I did find 3 frogs who decided to over winter in the upper pond rather than the larger lower pond. Despite the fact that the upper pond is only about 18" deep and developed close to 12" of ice over the winter, the frogs and 2 goldfish managed to survive till spring when I did the upper pond reno. I noticed the fish earlier, but only discover the frogs during the draining process which was done by me getting in pond with my rubber boots and bucketing the water out by hand. The frogs are luck I didn't step on them. I threw all the frogs and the 2 little goldies back into the lower pond. I know the frogs survived, because I saw them through out the summer, but I'm pretty sure the fate of the little baby goldfish was not so good. Likely they became a nice spring snack for the perch. It's kind of sad :'( that they managed to make it through the pump and into the upper pond and survive the harsh winter in that tiny pond, only to be thrown once again into the jaws of the lower pond,,, but hey, that's life.
I think the frogs chose the shallower upper pond to over winter rather than the larger lower pond because they knew there were no large fish or turtles to harass them while they slept the winter away.
