Would notice slight hint of green in my water during changes as well but after playing around with my photoperiod, found that 4 hrs on, 8 off, 4 on works for me. Adding floaters and stems helped as well. Have been able to even lower lights more now with no issues. Will continue to gradually lower further slowly and see what I can get away with.
Heh. My greenwater problem started when I added a siesta in the middle of my photo period. Took that out and the water is crystal clear. I can see the individual fish poops now!