I would like to see results with a sump packed with Marine Pure blocks. My meaning being a sort of extreme deep sand bed effect. Top layers with aerobic bacteria, and blocks 3 layers deep or so harboring anaerobic bacteria. Theoretically The top layers would have a faster water movement out of the sump, (path of least resistance) therefore carrying more dissolved oxygen for aerobic life. While the water that sinks down to the lower blocks would be slowed and the oxygen used up giving the anaerobic critters the right conditions to feast. If you get my rambling meaning.