Originally Posted by danbstrong
Looks like overflowing into your return pump raise water level in return pump chamber
Definitely... that water splashing down into the return chamber is creating bubbles that enter your pump & get chopped up by the impeller..... LOTS of micro bubbles. Bring your ATO up so that your water level is maybe 1/4" - 1/2" below the baffle. You want the water to flow into the return chamber, not splash into it.