Lost Shebunkins :(

When I went out in the morning, noticed the pond was very clear and fish were at the top. Realized I left the water running all night. Dot and Shadow showing signs of life, Pumpkin a little, but Nemo dead. All 3 Shebunkins dead by 9:00am. (Combination of chlorine and unoxygenated water) All old, mature water from last fall is gone, replaced by fresh water.