The biggest of these was about 2 inches long and as small fish are wont to do they were hiding in among the rocks and reeds at the edge of the water. The "pond" is actually a storm water collection site in amongst a great deal of houses. The pond connects via man made ditches to a small river not far away. With all the rain and snow melt we have had it is quite possible for fish to have swum into it. I, for one am glad to see them as they will keep the mosquito population in check.