Sound like Microbubbles. I don't know what causes them or how to get rid of them, but they certainly sound like microbubbles.
overfeeding is more of a problem than people think. one thing about fish is that they can survive for months without being fed. my tanks overstocked right now, so i only feed every 2-3 days, but i could be waiting even longer. really cutting it on feeding will solve your problems.
Just remember... Don't replace, run the old behind the new for a month then replace.![]()