I use a 50 gallon black plastic livestock tub with a ramp for my ducks to get into it. It's about 14 inches deep. We have tried 2-3 different kinds of filters to try and circulate and keep the water clean. It seems to get funkier in the summer heat than in the fall, winter, spring seasons. Has anybody had any success with filtering duck "pond" water. I have/had 3 ducks that used it.