Recently I built 2 self-cleaning ponds for my ducks and geese and now I am going to attempt modifying the design for a self-cleaning coop. My plan is to build a large box for the bottom with a pond liner and a large drain hole on one end. I will fill it with large pea pebbles and/or river rocks. The birds free range all day so I will use a pump from the lake on a timer to flood the base once per day just above the stones, and then have a drain valve on a timer also allow all the water and waste to drain away. If necessary I can use some version of a solar pool heater to heat the water for extra cleaning power. My research indicates there is no problem with the bird's feet and the smooth stones and I will make sure they are too large for them to eat. My question here is does anyone have any ideas on why this will not work before I try to build it?