Refer to my recommendations on the following thread.

http://www.pondboss.com/forums/ubbthreads.php?ubb=showflat&Main=5386&Number=49373#Post49373

It's much cheaper to use straight alum, if you can watch the pH yourself. And you could buffer it yourself, if you wished to save some money.

Regardless, I'd attempt the simple test described in the other thread sometime to see how much product can be safely used.

Holding a redear sunfish is like running with scissors.