[Octoman]

Prow, the dynamics you are talking about are accurate and have been heavily researched in the ocean. But that is occuring in a system that is stratified into different layers on the scale of 100 or 1000's of meters. The aggregation of bacteria and particles (the formation of marine snow) happens over time as particles settle to the bottom. This aggregation would never have time to occur in a home aquarium where any digestible particles are snatched up by pods, corals, fish, whatever else can nab them.

Also, even in very large fish tanks, the water is very well mixed from top to bottom (compared to the ocean). The dissolved nutrients are going to stay in the water column until they are taken up by some organism (or precipitated out chemically). What settles out in the sump/fuge is larger particles that have yet to break down such as fecal matter and left over food. What forms the film on top and is skimmed out is hydrophobic organic material. Dissolved nutrients such as nitrates and phosphates are not very effectively removed by a skimmer.

Bacteria can take up nutrients and are vital to the N cycle, but, as you know, they cannot remove NO3 in an oxygenated environment. However, algaes and zooxanthellae can. That is why I have the fuge with chaeto, to remove nitrate and phosphate from the water column.

I think that allowing particles to settle in the fuge or sump only allows them to be broken down and released as more dissolved nutrients into the water. That's why I prefer to use a filter sock to remove the particles before they get there. I don't think that having higher flow or lower flow in the fuge really makes a difference as far as the amount of dissolved nutrients in the water.