First of all, let me say that Plenums are good filtration. I have used them in many reef tanks. They work great. They effeciently convert N compounds to O2 and N gas.
Well, this morning I woke up as I often do, pondering aquarium stuff. For some reason a certain plenum was on my mind. It is at the bottom of a 400 gal tank in the Ivins City Town Hall. The particular image that was in my head was the hole in the sand under a large shell. These kind of depressions in the sand are nothing new to reef aquariums, but...
Hold on, this is sounding like a good article for the SeaStar.