Agree soilfloc is not perfect, read the forums, talk to TJ. I'm not aware of any risks to your pond life or water quality. Cost is trivial. Certainly cheaper than the amount you would spend on Bentonite. Most people with your situation just live with it and it always grinds them at the painful spot inside. But they know doing it over with the heavy equipment costs to do it right can be a 10 fold cost increase over the initial pond build or initial rehab costs.