K3 150 HOB micro bubbles after 7months of operating

Hello, I am currently using the k3 150 HOB skimmer and I have been running it for 7months now. It is a fish only tank. It does skim, but I am still getting micro bubbles in my display tank. Pump speed is on level 7. No kinks or pin holes in the air line as well. I wanted to see if there are any tips on getting rid on the micro bubbles? I can send a video over if you would like. I tried to upload it, but it keeps failing to upload. Thank you.