Hi bro.....
From the picture, i think is the Weipro skimmer....
You may want to check certain things here...
1. There is a water level indicator, is the water exceeded or below the water indicator?
2. There is a small pipe for the air to suck in when water flow through....Do you see any bubbles? If YES, try to place your finger to block the pipe intake...the buble should be gone...
3. Any major changes for before this happened?