K2-200 Skimmer

Hi Debbie, 9.5" of water is too high, please lower the water level inside your skimmer body to about 6.5"

Right now your skimmer is breaking in. During this period you should not attempt to dial in or set the skimmer. I suggest running the skimmer with the water level low in the skimmer (output valve all the way open) for the first 3-4 weeks running. You will likely experience abnormal air suction noise as well as inconsistent performance.

Your skimmer has oils from manufacturing and handling which will dissipate as the skimmer ages. Because oil inhibits foam production you will not see much foam produced from the air being injected. The hydrostatic surface tension of the water is lost. As the skimmer runs you will see point where it looks like it kicked in and is working as you would expect.

Please be cautious if it is prior to the 3-4 week mark as the skimmer could still be breaking in and you can experience and overflow.

The pump itself will run smoother as the impeller lubricates and the bacteria forms on all wet surfaces which will provide you with stability. Here are two great videos that may help you understand how skimmers work:

https://www.youtube.com/watch?v=EnwBrD2_Leo

https://www.youtube.com/watch?v=c7SNpKMD3K0

For the condensation you may want to get a fan, something like this will work great: https://www.coralvue.com/reef-octopus-usb-smart-fan
You will want to leave the water level low until your skimmer breaks in, after the break-in period you can start to dial the skimmer in by raising the water level or closing the gate valve. The silencer is exactly that, it quiets down the noise from the pump sucking in air. If you cover one or both of the silencer holes you are cutting off the amount of air going to the pump which reduces or increases the type and amount of bubbles. Here is a quick video that explains how to dial in a skimmer: https://www.youtube.com/watch?v=VCV2BU6sFJQ

That skimmer is a little big for your size tank but it should work just fine, just be careful not to over skim and monitor your nutrient levels.
All skimmers operate in the same basic way to achieve the same outcome, they just have different designs in order to achieve it. All a gate valve does is allow more or less water to flow out of the skimmer body. Think of it like a dam, when it gets too full for your liking, open up the dam to let some of the water out and vice versa. The gate valve on the K2-200 skimmer is just a different style; you turn the knob one way to allow more water out, turn it the other way to keep more water inside the skimmer body. The more water kept in the skimmer body the higher the bubble/water level will be inside the skimmer body.
The silencer helps regulate the amount of air going into the skimmer pump, the air injected into the pump is what creates the bubbles you see. The more air going into the pump, the more bubbles you will have. The less air injected, the less bubbles you will have. Not all silencers have a regulator on them, yours does, you can use it to make micro adjustments to the amount of bubbles in your skimmer by sliding the cover (the flat piece) over the silencer hole or, uncovering the hole completely. Again, they all work the same, just different designs to achieve the same outcome. I suggest playing around with your skimmer to figure out how each part operates, and to figure out how you would like yours to be dialed in.

I hope this helps... please let me know if you have any further questions.

Tightening or loosening the screw on the silencer doesn't do anything, it is there to hold the silencer hole cover.