That looks a tad wet to me, turn down the air by a long way, and then drop the skimmer down a touch
If it still skims very wet, cut more air, drop it a bit more, and then repeat. If it's dry, open up the air a little bit. By the top of the neck, the foam should be definitely discoloured. I told you those Boyu's were tricky to tune, and I'm sure in three weeks time when you are still tuning it you will start to agree
For a mantis, you want to cut the neck of an empty coke bottle, add your bait, and then put the neck back on the wrong way around, securing it with gaffa tape. Fill it with water and position in the tank. Mantis shrimp can swim, so will escape a cup in the tank. A coke bottle trap actls like a lobster trap. Easy for them to get into, harder to get out of. Cups are easy in, easy out... If you find you aren't catching anything after a night or two, enlarge the hole a bit more
The coke bottle will work for pistol shrimp also
All the best
Rabbut