Welcome S Brown. Hope you're here for the long run.
Have you considered adding alumnum sulfate? I currently have three ponds where the pH raises to over 10 every afternoon. Here's a link to a thread that discusses alum application, how to do it, and what effect it may have on your lake or pond.
http://www.pondboss.com/forums/ubbthreads.php?ubb=showflat&Main=5386&Number=49373#Post49373I'm not necessarily recommending this---just throwing it out there for discussion.
By the way, my ponds are entirely filled with well water. My fish thrive 99% of the time, but sometimes there are issues with pH that arise from the high alkalinity, conductivity and pH that come along with the groundwater.
Bruce
