Before you buy new water, test your water first to see what is in it as it may be fine. In general, well water often has desolved metals in it that you don't want in your tank as well as run off water depending where the well if actuallt getting the water and where you live.. RO water is just a type of water that has been filtered in a certain way taht created 99% clean water. I buy my water at Walmart. The distilled water there is about 45 cents a gallon and is OK for saltwater. Though I can see using this would make a large tank quite costly. You can buy a RO filter on ---- that can create 10 to 15 gallons a day of perfect tank water for about $65. But first, see if you can find a local LFS to test your well water before you put it in your tank. A saltwater LFS should be able to tell you, if this bloom is caused by your water.
Still, I think the problem is more related to your lights and boi-load than anything else. But it never hurts to test your water to see what is there.
Steve