I had asked a question yesterday in a different section of the forum about fixing water quality issues in my fish pond, and someone suggested that I add a bog. Initially I thought about adding a small bog to the filtration system that I already have, but after reading up about bogs last night and today, I think I want to completely replace my current (large, ugly) DIY two-barrel bio-filter system with a larger bog as I think the bog will be much prettier. I'm excited to be able to add some new and different plants, too, since the koi pretty much eat everything I've tried to put in the fish pond except for a few floating baskets. My fish pond is in an old cistern, 9'x9' square with a sloping bottom ranging from 2' down to 5' in one corner. There's a waterfall above the deep corner. The current bio-filter also has a UV light attached. I thought I would take a second pump and the UV light and use those to circulate water just for the waterfall, then use my current pump to circulate water through the bog and back into the pond on the opposite side from the waterfall. Would that work, or should I just ditch the UV filter and have the waterfall source from the bog? I'm limited on where I can place the bog, the only place it can go is along the side of the pond opposite the waterfall, but I can run PVC around to the waterfall like I currently do for the barrel filter. Because the top of the cistern is 18" above ground, the bog itself also needs to be above ground at about the same level or higher. Which works out, as I already have a metal livestock tank that I can use - it's 6' in diameter and 2' deep. The recommendation that I've seen, though, is to make the bog depth 12". I order to make the tank 12" deep I'd have to backfill with sand and then add a liner, which is a big expense, plus I'd have to find a way to hide the liner somehow. Would the bog still work at 2' deep? Or could I maybe add bigger rocks at the bottom, then the pvc pipes, then 12" of pea gravel on top? Since the bog will be above ground, do I need to do anything in particular to make sure the pipes don't get damaged in winter? I'm on Maryland's eastern shore so we have fairly mild winters. We do get a hard freeze now and again but they don't last long - there's sometimes a thin coat of ice on the fish pond that melts away in the sun, maybe the occasional winter storm that rolls through with some snow and ice for a day or two, but rarely anything too severe. I usually drain the barrels of my current system once the fish go dormant for winter and just use a circulating pump for aeration. Would I need to do the same with a the bog? Would my plants all die off in winter if the bog is dry? Any thoughts would be appreciated!