Thnaks all bro & sis,
Decided to change a new power head. had ask around some fish shop, they say it's the power head problem. currently using Rio 5000, they say pump to big for my 3ft tank, they advice me to use 3000 or 4000. live rock inside tank. thinking of getting a 2nd hand power head.
Here again thanks all bro & sis giving me advices & helping me along the way. Next time if i encounter problems again, hope all bro can give me aadvices.