Hello,
We are new to outdoor ponds. We built ours late last year and seem to have a nice clear pond until we added snails and plants we ordered online and then everything went south. We ended up cleaning it out entirely finding rotted plants, snails and fish. We refilled it this spring and added beneficial bacteria, algae fix, salt, barley and new aerators. We have a 2000 gallon pond with levels at 1, 2 and 3 feet. We have a waterfall and two small aerators as well as a skimmer. I would have to say we have gone through a dozen fish and continue to have problems despite not having poor PH, Nitrite, Nitrate or Ammonia. We have tested our water 3 times and each test came up with a PH of 8.2, the Nitrite, Nitrate and Ammonia were all 0 ppm. We only checked the temp once and it was 68 degrees at around 7 pm. Our pond only gets am shade due to it being located just west of our house so it gets direct sun from noon till sundown. We have 3 lily pads, 3 hyacinth, and 3 horsetail rush. We have no idea what could be killing the fish-so frustrating. The one thing I have noticed time and time again is that when we see the fish, they are lethargic, hovering around plants and constantly gulping for air. The other thing I noticed with one fish is it seem to have a stringy white film on its body and it kept popping its head out of water and the tail was down.