Thanks FBNitro.
My tank was under recycled since Dec 08. First month with no light, then 4 hrs frm mid jan then 6 hr frm Mid Feb (because my wife brought home a strange softie pc that needed light to stay alive, and it doing ok as I know for now
). Now I have it run 8 hr per day (8 and half for the blue atinic that I heard it needed to be over lapsed with daylight a bit.
So I guess, I am doing ok with the light I have. But having saying that, when changing light, I'll take your advice to have a mixing change of 1-2 buld at a time.
Thanks for your help FBNitro.