Thanks. I already fixed the problem by connecting a tube from the collection cup to drain the bubbling water out. Then, I replace new water back in the tank. I think that I used to much glue on the rocks, so the skimmer made too much bubbles from the glue chemical.
I don't want to burst your bubble because I've been where you are. I had the BH1000, it used to pull the darkest skim mate. I loved the thing. Until it overflowed for no reason at 2am and almost burned my house down. The result was me tearing my entire tank down and upgrading to a sumped tank. (Thousands of dollars)