I have a half acre pond near Steamboat at about 7,500'. Planted fish in it last year and they grew like crazy. Was great until 10 days ago when they all died. Some floated and some sank. Pond had a pretty strong crop of moss but it also has an aerator. There's another on the neighbors property that gets water from my overflow and all his died too, about a week before my dieoff. He has no moss in his pond. Anyone have any idea what would cause this or know who to call? Thanks in advance.