I maybe way off on this. But dosnt the air push the algae away? That would mean your are putting the chemicals farthest from where you need it most. My personal opinion is you would want to go along your bank more so than the middle.

The people who say I can't do it can just sit the @^#% down and watch me. Friends call me Rusto I also subscribe to pond boss mag. http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=504716#Post504716