I just thought I would post a few pictures of our pond that now has the fish in there but we are not done, as it is now the top has just the liner overlap since we are going to build a structure around it and we are going to tile it.
At the moment just a homemade filter and one uv which I think needs the buld replaced and we have another filter with a built in uv. We are building a filter system that contains 4 55 gallon plastic drums. We did not put bottom drains in but will be doing a retro bottom drain on eac end and maybe in the center. I have a skimmer we are thinking of adding but are holding off just deciding because if they spawn they may end up in it.We have the area for the bog garden in the works but with the hours my husband works it is a slow process.
We get full afternoon sun so I am not to worried about the crystal clear water until we get the roof over it. We do water changes a couple of times a week to adjust for the lack of filteration until the barrels are done. I have koi in there that range from a few inches to 30 inches.
MM, Use the stock tanks. I had a 75 gallon stock tank, upflow lavarock, gravity feed out for 3 years with out any problems on my 5k pond. I figure you could use a 300 gal stock tank, or several little ones. It depended on what size waterfall you want. If I'm ever down that way, I'll have to stop by and visit.