Please read this post, there are many others too...

http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=471097

If you don't use it at the right time and in the right way in the pond build process it may not give you the desired results.

Just want to save you hassle and expense. It isn't as simple as dump on and it 'seals'. Rainman is a good resource as is TJ