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RE: Wet/dry filter
>>>As far as increasing oxygen to the water the old fashioned airstone is still hard to beat in terms of simplicity and cost.<<<
FWIW, Jim Robinson presented his continuous flow, central filtration system in Cincy a few years back. One of the interesting components of his system was a tall 4 inch PVC pipe used for returning overflow water from the top or the rack. The excess water that overflowed from the distribution manifold is routed to this pipe and returned to the filter sump. The pipe is filed with plastic bioballs and has an airline snaked down to the bottom (no airstone). The purpose of the bioballs is no to provide biological filtration, but to tumble the water as it cascades over the balls. The increased surface area of the small droplets allows for greater oxygen absorption than a solid column of water. The study gave the optimum height (I think it was 5 feet, but I'm not sure). The AKA video library has a copy of his entire presentation, BTW.
Now I doubt this is the type of fixture Wright's wife would agree to in their living room, but it may be useful to others or elsewhere in the home.
FYI, an airstone is an effective technique to oxygenate as well. It's actually using the inverse of the above technique. Jim's column creates additional surface area on the outside of the water droplets, while an airstone (with small bubbles) creates additional surface area on the outside of the air bubble.
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