I often wonder just exactly how many fish live in our pond. I sometimes sit and watch them swim and try to take a census. The problem is, even when fish go slowly they are moving quite fast... even when they seem to be floating and sunbathing they are still moving. It makes it hard to count. This is complicated by the fact that the vast majority of the fish are brown. They are hard enough to see at the best of times unless the light hits the water just right - and apart from variations in size, they all look the same!
See what I mean! All kind of brown with no distinguishing features. Very hard to tell one from another. It is supposed to be quite hard to breed fish - but ours have managed OK. Although the population has been added to over the years I should think that around two thirds of the population were born and bred in the pond... maybe more if we account for the few that have been buried over the years and the proportion eaten by the heron back in the spring.