So I decided to construct a new pond. A big one. About 3500 gallons. I finished the hole late in the season so rather then spend the money on a black pond liner I decided to do something cheaper. I received a Namco Swimming Pool liner for free so I used that for now. I have a UV light and the biggest Tetra Pond Gravity Filter they make. I lined the edge and shelves with river rocks found locally. They were pressure washed and set out in the sun for days. I did a vinegar test on them and they did not fizz. Water lilies and floating pond plants thrive. The pond is a little over a week old. I decided to add some feeders to get the filter cycling. Within 24 hours all my fish were dead. The water temp is around 75 degrees. Ammonia is none existent since fish were not in there long enough, PH is around 7.5 and KH is around 175. I'm pretty sure these levels would not kill fish. I'm wondering if I played russian roulette with my free pool liner and lost? Could toxins be released from a brand new pool liner and kill the fish? 
