4 thoughts; Have the skimmer discharge into the left most chamber to keep microbubble issues to a minimum. Secondly, don't use magdrive pumps externally, they get really hot, and are prone to seal failure. They're really best reserved for when you have no space and have to put them inside the sump. Replace them with similarly sized true external pumps. Third, use double unions on the ball valves before the inlets to the pumps (one on either side of the valve). That way whenever you have to break down your tank/sump for whatever reason you don't have big bits of plumbing sticking off the glass that are a pain to remove. And finally, consider using a filtersock at the drain instead of mesh/carbon in the bubble wall. Will eliminate the need for filters on the pump inlets which will make your overall maintenance less of a PITA