aqua euro calcium reactor question

[eshark]

I purchesed the 135g model and i like the design and the function of it however my question is the PH! In the reactor the PH is 6.9-7.0 and my calcium stays at 400-410. I would like to bring the calcium to closer to 440. Should I lower the PH buy increasing bubble count of CO2 or slow the flow rate down going back to the sump for more contact time?

http://www.aquaeurousa.com/Calcium_Reactors.htm

Thanks in advance!