The newest instructions out for the coralife skimmer has it so the outflow tube is "AT" or slightly above the tanks highest water level...not under it.........and also the pump shold be raised up as close as possible to the surface 1.5" or so....As tempting as it may sound its not recomended to put any additional tubeing over the outflow "air bleed"
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on the outflow pipe. The purpose of this
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is to allow water to flow out of it if the outflow diffuser foam /filter gets clogged, and also to purge some air that may be trapped. Putting it under water does not really serve much n the way of stopping micro bubbles as its not a venturi and the flow is insufficient to pull any amount of air into the outflow waters discharge.........Same thing with e air intake tube off the silencer...do not add any valves etc to try and reduce noise....If skimmer is setup as stated above it will be quiet. One big change not mentioned by coralife is the big ugly bubble diffuser box...Chuck it in the trash and do without. Get a foam filter sleeve like is used on the MAG 3 and 5 pumps over the strainer. Place this on the end of the outflow tube with a small portion of it in the water and the rest above the water line, or in the case of a 65 CSS simply push it up on the elbow.........After those changes to the diffuser box, you will not have any big ugly box. Adjust the bubbles in the reaction chamber so that they are about 1/2 inch or from the bott9om of the collections cup funnel portion, or in the case of a 65 size about 1 to 1 1/4" up from the red ring used to secure cup to reaction chamber......This will eliminate 99.9% of micro bubbles, eliminate any leakage around the adjustment knob, and just about make it as quiet as a church mouse.........Its a terrific trougle free skimmer, but its too bad Coralife screwed up and did not do a good job on printing up a proper set of instal and setup instructions. They intend to have these new setup instructions on their website and its in the works so I am told........
Odds are that when yuor skimmer is setup properly, and running that the red adjustment knob will be no more than 1/2 of the way rotated from the fully closed position or the little nub for a ppointer will be at about the 6 oclock position. Just because the knob turns more does not necessarily mean it has to be run at the wide open position to be doing its job.........Once setup you will be getting some nice dark black/green skim off it, and it will be a slightly dry skim. If your wanting more wet skim raise the column of air bubbles closer to the bottom of the funnel portion of collection cup, but be prepared to have to empty it on a daily basis and add more top off water as well........