Well I would suggest that any RO water is an improvement from tap water. However, the only problem it really solves is making sure that you are not importing nitrates and phosphates in your water, it does not cure those problems from other sources such as feeding and livestock. All algae I have read up on thrive on excess nutrients in your tank so the only real way to eliminate the problem is to control nutrients. Effective skimming and some form of phosphate export are a beginning, but I don't believe overnight results are to be expected (never had such a quick result in my tank at least). I have read numerous other strategies to combat algae, as well as some opinions that no matter what parameters are kept some algae blooms will occur. As far as the water goes you may even read some places, such as on WetWebMedia that deionization is more important than the reverse osmosis process. However, I think no matter which opinion you read you will see some correlation between nutrients and algae. Nutrients have to be controlled at all steps in the process, not just import through your water source.