The tubing from the cup to the venturis may act as a silencer, but I think the main reason is to collect fresh water condensation from the moist air inside the cup. It then drips down the through the venturi, helping to lessen clogging from salt creep and to help keep the venturi clean. That is, I believe, an old LifeReef design. I know their skimmers have had that feature for a while. You will see beads of moisture form inside of the tube and run down into the venturi. I wouldn't put any sort of air valve in-line, as it is not necessary and will only restrict your air / water flow to the venturi.
BTW, I missed out on this thread somehow. I didn't lose my reef to Katrina, it was Rita (the other huge storm that everyone forgets about) that came only 1 month after Katrina and hit the SW corner of the state of Louisiana and SE Texas. The storm didn't get the tank, it was the power outage like Lukinrats, except our power was only out two weeks.
AND, I really didn't teach OSB anything. He is way ahead of me and even has a bigger, nicer tank than I do.
