ok here's what happen.
1) Brought a T5 lighting 2 x white , 1 x pink, 1 x blue at jan.
2) There's no green algae at sight using the old 4ft lighting.
3) after installing, i notice the green algae starting to appear (thinking the light is feeding it)
4) 1 month later, the live rock which is brown turns into this colour. (only this liverock). rest is still brown and some purple (seed for purple up to help me blllloooooooooom)
Its nearest to the return pump so i think it might be the cause of the top up water (non di/ro) , using tap water to top up after resting it for 5 days.
At Feb, starting to dose
SeaChem Reef Buffer (to up my ph from 7.9 to currently 8.3) 5ml raising 0.1 to the 4feet tank per day, thats all
Rest is topping up with water.
hmm, thinking of moving the rock to my sump to it from exposing to light <-- does this help?