You can improve your water quality by doing several water cahnges with ro/di water. You don't have to start from scratch. The main things that promote alge grouth in tap water are phosphates and nitrates. You can reduce these by both water changes or by filter media that absorbs them (I've use PhosGuard to get rid of phosphates, and I think there is another chemical that does the same thing for nitrates). If you do 20% RO/Di water changes every couple of weeks for the next couple of moths or so, you should be able to lower them significantly. They will still accumilate naturally in your tank from fish waste and feeding, but a regular 20% water change once a month would control that after you get it to the normal level.
There are other factors that contribute to alge blooms. One is lighting: make sure you have the right spectrum (10,000k and actenic blue) and that your lights are not too old (the spectrum starts shifting after 5 monthts to 12 months depending in the bulb brand). Also, DOC (Disolved Organic Carbon) in the water is food for alge. This is basically protine disolved in the water from overfeeding or decaing. Your skimmer should get rid of that.
72G bowfront reef
175G bowfront cichlid tank