Water Chemistry & Algae

I have recently retro-fitted my 150 gallon aquarium to grow plants.  I am currently battling a severe algae bloom and have a few questions for the chemistry guru's.  First, does an alkaline ph promote algae growth as apposed to a PH less than 7.0.  Second, I'm on well water which flows from the tap with a ph of 8.2.  I have two DIY yeast CO2 generators running into a power head during lighted hours and the ph drops only to 8.0.  What in the water could be buffering the CO2 so much?  I am considering an RO to clean up the water a bit, will RO water eliminated this buffering effect.  I have recently lost four angels for no apparent reason, since starting the CO2 injection.  Since there is little change in ph, what other effects could CO2 injection have on the angel fish.  I have introduced no new fish, my nitrates, nitrites and ammonia levels are off the scale on the low side.  I do at least a 40% water change every week.

Thanks in advance.