Mike

I built the same system RC51 has and love it. cheap and works great. I have it hooked up on a dawn to dusk timer and has been working great. My DO has been between 6 and 8 PPM. work at a waste water plant so i have accsess to testing all parts of the water here is a link to what I have set up in a 3/4 acre pond 14 to 15 foot deep.

http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=248108#Post248108

A weeks worth of vacation, 59 hours in a John Deere 160, 2 logs of Skoal, 1500$ in fuel, Lots of help from the neigbors and my old man, and a wife with an open mind to let me dig a pond at are cabin. All i can say is life is good!