I building my duck run and coop this week for my four Welsh Harlequins and I have a bunch of materials that were given to me or I have already kicking around. One of those items that I have is a Rubbermaid 300 gal stock tank with a drain plug on the bottom. Initially I was not going to use it as my duck pond for a couple of reasons but the more I think about it it seems foolish not to but I have a couple of concerns. The first is that it is 25" tall, will they walk a ramp up to it? Second, 300 gals is a lot of water that I do not want to change daily. If I get a little pump and make a filter can I let the water go a week or two? I use the water to water all my plants so I know most of it would not be wasted unless I have to change it daily. I do have a couple of small koi ponds so I know how to make the filter. And third it is 5x6 feet around, is that going to take up to much space in my 12x16 run with a 4x6 coop in it as well? I would think the ducks would prefer pond space. They will spend most of their time in this area and will be allowed to free range in the backyard when I am out with them but my koi pond in the yard will be off limits.