You have to keep us posted on this, I am reluctant to use a product like this to fix my seeping pond, but it may beat a complete drain re-do. I don't want to loose all of my fish in the process of fixing the seepage, but the way this product works may be effective in my case.
I would suspect that if a pond is "connected" in any way to ground water and the flow through the soils reverse direction at various times of year, ESS13 applied to a full pond wont be much help as it will get flushed from the soil or never make it into the soil to allow compaction. Also if the shape of the soil grains is such that the ESS13 does not help it compact, then all bets are off too.
I would make a bet that it is very difficult to predict scenarios where this product will work, and Seepage Control is in a very difficult business I don't envy at all. I hope people come to this thread and also post successful results, but I know how rare it is for people to post positives vs. negatives. However if it does work for your situation with minimal fish loss, that is great! I for one would love to hear it.
For me I have very hard water to the point of when ice forms, lime precipitates out. I think I have a chance of applying rock salt to my pond for ion exchange to produce a similar effect of ESS13 if water truly is seeping through my soils. The ion exchange should allow the soils to become more "fluid" and compact rather than clumping in little ionic wads. Also the fish may actually like it as long as I don't overdo it.
