As a side note....what do you have supplying water to the reactor. Your input water pressure could be too high. Do you have 10- 15 psi on the gusge feeding the needle valve?? If you shut off the reactor and disconnect the line from the bubble counter to the reactor, do the bubbles restart, also place the end of the same hose into a glass of water to see if you still get bubbles(do not place end of hose into the tank...that could drive down your Ph)?
Cheers,