[sphelps]

Mr. Wilson, I'm slightly confused by your post and was hoping you could clarify.
First, only external/recirculating skimmers have an adjustable turn over rate and none are traditionally gravity fed, unless by gravity fed you simply mean with a pump because no skimmer should be run off gravity (such as straight from overflow) as it will never produce constant flow and cause the skimmer level to be either too high or too low. Also building a separate skimmer chamber which requires a pump to feed water out at the same rate of the skimmer is a new one for me, I have never seen this. The 10X turn over recommendation is based on tank/sump flow and not skimmer flow, I have never heard of someone running 10X tank turnover through a skimmer before. Today's skimmers are not co-current, air stone powered tall structures. They mostly use a single pump and do not offer flow control. Lastly sumps should be designed to handle the tanks/owners requirement for flow, this is fairly simple and eliminates things like mechanical filtration bypass and would provide adequate contact time for carbon.