Hello everyone, I'm getting ready to build a 400 gallon duck pond. I already bought the liner and pump. I kind of have it all worked out in my head already. The deepest part will be about 18 inches deep with steps along the edge. I would like to be able to have some aquatic plants and maybe a couple gold fish in there if possible. I know the ducks will poo in it but it's going to be in ground, so natural filtration would be awesome! Does anyone have any tips?