[papagimp]

Well, the problem is most likely due to using a 20g for a sump with a quiet one 4000 as a return. In other words, too much flow for the baffles to work properly. A lower return pump would probably help but that's a tad expensive for a fix. I use a foam prefilter (cleaned regularly) on my mag12, it makes a big difference in microbubbles returning to the display. I also occasionally run a filter sock in the sump, that cuts out every single bubble even prior to reaching the bubble traps but unfortunatly a filter sock would require almost daily cleaning to avoid the negative effects they can have (high nitrate levels). Those are some idea's to start, we'll see if anyone else has some bright idea's though.