About a month ago I had a heron get into my ponds which I have two and ate all of my fish my top Pond had 8 small bluegill in it that my son had caught and I've had them for a year my lower pond had about 28 goldfish numerous sizes some I had for three years others only a year or two anyway I thought that all the Goldfish were gone in the lower pond and because of health issues I hadn't changed the water. The water got murky was very green you couldn't see in it but the filter was still going barley.so two weeks ago I cleaned out the top pond because I was going to buy new fish. Well my son put about 20 minnows in there he had left over from fishing. They started dying off I don't know why because the water had been filtering about a week with nothing in it. So after all of them were dead I decided to clean both ponds yesterday and start over. I cleaned the top pond put declorinater and algie fix in it. So I started draining the lower pond and found there was 1 bluegill and 5 goldfish living in thay nasty green murky water . so I got the Goldfish and bluegill out of the lower Pond put them in the top pond how they survived in that water I have no idea. I put some buckets with rocks in the pond so that they can go into hide until I could clean out the lower Pond that had the lily pads. The buckets had been use in the ponds before I just rinsed them with the rocks they have been in the ponds for many years. So I went out there this morning and they're all dead again I don't know what's wrong with my water if there is something in my water how do I find out to test my water what should I do I don't want to put any more fish in there until I find out I still haven't seen the bluegill but I'm sure he's not doing well either I need help to find out what's killing my fish I know the Heron did the first time but what killed all these fish that have been put in that pond and the pond water has been cleaned twice I've had ponds for about 10 years so I know how to clean it I know how not to clean out all the beneficial bacteria I don't wash the Rocks I just rinsed the pounds out and drain out the water put fresh water and put the correct chemicals in it that is supposed to go in there. I am so hurt that these fish that survived the heron been living in nasty murky water . I put them in a nice clean filtered pond and they die. Please help...