So I just did a water change today. I turned off everything and my skimmer too. I cleaned out the cup and take the filter socket on the back and change a new one. I was having trouble to take out the cup so I guess knock it a bit but not alot (very gentle twist). I filled up the water and everything and turn it on. But the skimmer is letting out this air bubbles on the valve. Should I be worried? Last time I did it and there was no problem but this time is different.

