First, make sure none of these items are in use, these will affect surface tension of the water and result in wet/uncontrollable skimming.
Seachem Purigen or other organic exchange resins, since these resins are intended to do the same job as a skimmer on tanks where a skimmer is not feasible, there is no reason to use it with a skimmer.
Non phenol free floss or socks (basically if you are using a media not intended for aquariums, it will usually contain phenol and this will cause the skimmer to go crazy until it is broken down, which usually takes a week or so)
Any organic additive, dechlorinator, stress coat, vitamin and amino supplements, carbon dosing, medications, algaecides. All of these will cause foam overs, their is no reason to use a water conditioner if you use RO water. There can be viable reasons to use the other products but when medicating or treating algae the skimmer should be off, for carbon dosing wet skimming is part of how the process works and for vitamins and aminos, a regimen of half the dose twice as often will reduce the negative effect on skimming.
If none of these apply, keep in mind adjustments are not instant, they take hours to show, be patient. Make an adjustment and wait. I am not familiar with this aquarium so assuming the water level stays constant in this chamber, I would start as follows. Unplug the skimmer, open the air all the way. Set the skimmer so only 1/3rd of the intake is submerged, keep in mind that if less than 1/4 is submerged the air control does virtually nothing, the skimmer has unlimited access to atmospheric air and is starved for water. Do not submerge it so more than 1/2 the intake is submerged and this depth must remain relatively consistent. Plug the skimmer in and work on the on the air adjustment. You generally do not want to exceed closing the air more than 1/3rd of the full travel of the screw, as you reduce air flow, water flow increases, the pump will pump the same amount, you are adjusting the air to water ratio. If you still have wet skimming with 1/3rd submerged and 1/3rd air closed, you could raise it a very small amount, about 1/8" or so. Beyond that I would dispose of the cup contents, it may be there is a surfactant substance in the water and you just need to remove it, after a week if no more of the substance is added, it will be removed or broken down, fresh activated carbon may help. Feeding foods that are high in cellulose/chitin and low in fat can also help a skimmer break in and absorb substances that may be causing problems for the skimmer, freeze dried krill is particularly good for this purpose.
