I have a fairly large koi pond with two waterfalls. I have discovered that both leak between the biofall waterfall lip and the rock spillway. In both cases the spillway rock is a uniform one inch thick flagstone mounted on top of the waterfall lip and sealed with foam (Great Stuff). The rock appears to be sealed around it’s entire perimeter which will make it very difficult to move. What I would like to do is seal the area between the waterfall lip and rock with silicone. Will this work? What are the pros and cons versus using foam. Thanks, Ellis Smith