DKoKoMAN’s 305g Basement Reef

[gregzz4]

Sounds like it’s not getting enough air. Not familiar with your airflow adjustment but check it to ensure it is open enough, or open it more. The more air it gets, the lower the water will be. If that’s not working, remove the Venturi from the volute and air line, and check for calcium buildup or a blockage. Also inspect the impeller in case something got in it.
Keep in mind too much air will cause it to surge up and down, and cavitation can damage the impeller.