It sounds like the small volume of water you had left was choked up with the polymer, leaving no room for the fish. If I understand the chemistry correctly, it reacts with a great deal of water to create "snot". If all you have left is snot, the fish are going to have a rough go of it.
Also the only leaks you will plug will be in the basin where there is water to carry the snot into the leaks. That means right now, you probably have a very well-sealed bottom basin, but the side-walls will likely still have leaks that will need to be addressed.
What I wonder if if the materials can be tilled into the soil on the exposed sides, and as the pond fills or it rains it will be effective in getting those areas currently above the water line?
