Water chemistry and plants

Question
I have a newly set up 70 gallon aquarium (36" wide x 18" deep x 25" tall).  I've stocked it with a variety of 45 plants and it's been in operation about 10 days.  (I just added my first fish: 2 clown loaches to take care of the snails that came with the plants ;)

It is illuminated with 234 W of 6500K bulbs.  I also have a do-it-yourself sugar-yeast CO2 injector, which is unregulated.  There are several pieces of mopani wood, and I filter with a canister filter that has activated carbon in one of the stages.

My question is regarding the water chemistry.  I have well water which has these attributes:
pH: 7.4 - 8.0, depending on the day; TDS: 193; GH: 358; KH: 358

I also have a reverse osmosis system on my kitchen sink.  The water from that has these attributes:
pH: 6.6; TDS: 12; GH: 17.9; KH: 35.8

I keep 10 gallons of each in jugs ready for water exchanges.  

I like the lower pH of the RO water, but I like the higher KH of the well water.  Which water should I use?  Will the well water with it's high pH and high GH adversely affect the plants?  I plan on a community tank with all sorts of fish eventually.

Thanks,
David

Answer
Hi David

If the well water pH fluctuates between 7.4 and 8.0, and the RO water is a steady 6.6, I would use the RO water. Your plants would likely be fine in either, but sudden changes in water chemistry can shock and possibly kill your fish. Also make sure you are using a good water conditioner such as StressCoat or AquaSafe.

Hope this helps, good luck!

Richard