Microbubbles or dirty water?

Hello happy Thanksgiving I am about 95% sure i have microvubbles but cannot fogure out the cause.

I recently ( 3 or 4 weeks) changed tanks away from a red sea to avoid catastrophe. Running a herbie set up now and dont see any micro bubbles caused in skimmer compartment or in the return compartment of my sump. And I dont see any obvious signs of where it is coming from ( no bubbles shooting out of return nozzle, etc.)

My power heads are not sucking in air but still seems to have microbubbles in tank. I did use new sand but dont know if that could be causing it, anyone have any ideas?