I recently added a pair of ducks to my flock of chickens. Everyone seems to be getting along fine, except for one small matter. The ducks play with the water, emptied a 3 gallon poultry waterer last night. I thought moving from a watering bowl (that I used when the ducks were by themselves) to a poultry waterer would likely fix the problem, but no. Any suggestions on how to keep the drinking water in the drinking water vessel?