hi guys, thanks for the insights and input. I did add about 100 drops of CHEMICLEAN a few days before to remove some RED SLIME, but this is not the first time I am doing this. It happened after turned on the skimmer after about 48hours later. I did a 20% of water change as advised by the producer, but no joy.
I also tried different adjustments to the water level and air flow, took many hours experimenting it. Still no joy.
As for food, nothing out of the ordinary that i have noticed...
The latest update, as of Sat, the bubbles are a lot lesser now and is skimming but not as efficient as before...at least it's till working. Will see how for next few days. FIngers crossed..thanks again...