Well it's still a fairly new tank and with switching you water it may just be adujusting. I would cut back on the light cycle (don't know what yours is now), but that would be a start at controling the algae a bit. Possibly cut back the light cycle a half hour on both ends every couple of days until you find a happy medium. This is what I did until I had my algae under control and once my macro started to thrive I slowly increased my light cycle where I wanted it. Increasing your macro algae would also help.

Good luck. RO/DI is the way to go and normally tap water causes algae blooms so be patient and allow the tank to adjust to the new water. Once your water is predominently RO/DI you shouldn't have any problems.