I have a friend named Greg Wittstock who has an Aquascape pond of probably an acre and a half. Maybe larger. And in this pond there is a teeming ecosystem of turtles, fish, plants, insects, and amphibians. If a fish were to die of starvation in his pond, we would have to assess the fish as being brain damaged. There's plenty to eat. Many of the large Aquascape installations will have a goodly amount of live food and plant material for the fish to be sustained on. This is great from the standpoint that you can feed conservatively, and if you are ever away or forget to feed the fish chances are they'll find something juicy in the gravel or they could prune your plants. Foraging in the gravel is an important way that fish prevent that very gravel from stagnating. (Or you can toss a pair of boisterous kids in for a weekly summer swim like Ellen B. in Batavia does.)