My koi pond remains murky, can't see the bottom. The goldfish pond is crystal clear. Beginning to wonder if koi vs. goldfish is the main reason, but this spring/summer I intend to add a very large bog to the koi pond, and then I will know if it is the very large bog on the smaller goldfish pond vs. the very small bog on the much larger koi pond that is the difference. Have had the goldfish pond running all winter (bog, skimmer runs the stream, and pump as a water bubbler, to keep the opening in the ice), and koi pond bog and waterfall had to be shut down in first week of Jan., first arctic blast this winter, and just got it back up and running this past week. Hoping things will clear up in time, and when the plants start growing, I'm sure it will clear up, as then the beneficial bacteria will begin doing it's job as well.