right now my goose and duck have a small 3 ft kiddie pool which is only 6 inches deep. i am looking in to either getting a 150 or 300 gallon stock tank for them to swim in instead. this way they could use it during winter, i wouldn't have to dump it and although its 10 times more expensive it would last longer. i am planning to have it on a hill so the drain is exposed but in the other side it is ground level. then i will make a little rock wall around each of the sides but leave on side open. their will be either steps or a ramp so they can get in and out. do you think this eliminates the possibility of drowning? and how often would i have to refill it? does any one else use a stock tank for their geese or ducks?