CO2 woes

Hello, I'm a recent subscriber to this list, and I'm about ready to pull my hair
out over co2!! I have a 110 gallon planted tank (w/ two 175w metal halide
lights)  that was set up in Dec.  For various reasons I wasn't able to get CO2
added to it until a month ago. I'm using a Sandpoint controller with their co2
system and I'm having a very difficult time keeping the ph stabilized.
  My tap water has a KH of 3 (tetra kit) and ph of 7.1.  Before the co2 was
added the tank water ph was swinging out of control (7 to 8 one day 8 to 9 the
next) and KH was dropping to 2.  I have the controller set to turn on the co2 at
7.3  w/ a bubble a second.  It works great for a day or so and then the ph
starts climbing to 7.6 and above.  I keep swearing at the reactor, but maybe
that isn't the culprit?  The Sandpoint reactor has been very difficult for me to
regulate. When I first got it, it was next to impossible for me to find a
balance between enough water flow going through the reactor and blowing the co2
out of the reactor.  I'm using an Aquaclear 802 powerhead (the 301 wasn't
powerful enough).
   This is driving me crazy, every day I'm fiddling with the co2.  Should I just
not worry about the rise? Or is my reactor just not very efficient? If it is my
reactor, can anyone suggest a better one?


Sharon Stewart