I just got some koi from a friend and now my pond is a muddy mess and stinks and my water lilies are dying. Do I need to clean the whole thing out and start over?
First of all, your koi are eating your water lilies. And the fish waste is making the pond stink. If you give the koi away and get a couple of plain goldfish and then balance your pond ecologically, you will have a clean pond that is relatively maintenance free. Yes, you do have to clean it out and start over. Sorry.
If you wish to keep the koi, you must add a biofilter and feed your koi.