I'd make sure to do a phosphate test on it as well before going further.
Phosphate = algae food.
Also, I'd at least call the water quality people in the area (not sure what to call em..whomever does the water cleansing for your tap water..) and ask for a water quality report.
It'll give you the various stats on the other stuff in the water (like copper, which is a good thing to keep your eye on).
Most will say go with ro
but I'm sure there are plenty that use the plain ole tap water. Depends on the end results you want.
Personally I want as 'virgin' a setup as possible, so I went ahead and got an ro
unit off ebay (works great for cooking and drinking water too!)