Aqua C
Hey. I have been using an AC EV-240 with a large pump for over 10 years. Indeed it is sensitive but once you get it going it pulls the most discusting stuff imaginable.
Patience is the key.
First shut off the air valve almost completety. This is the up position. Now open the gate value as far as you can with out flooding the top of the skimmer. If you can open the gate valve all the way (without drowning the top of the skimmer) then that tells me that your pump is NOT too strong.
If it drowns the top of the skimmer at this point then your pump is too strong. If it doesnt drown the skimmer then leave it alone for 24 hours and observe.
If after 24 hours it starts to skim, then you're good to go.
If atter 24 hours it still doesnt skim, let more air in by lowering the air valve. Just lower it a very little bit and again wait for 24 hours to observe. Continue this process until it starts to skim.
If you reach full air and the gate valve is wide open and it still doesnt skim then, your pump is not big enough.
Aqua C customer support is great, send them an email.
One note. There can be no back pressure on the return. The water must flow out un obstructed. If you need to put an elnow on the return, either provide some air, using a T, or do it gradually. If there is any back pressure, you'll flood the skimmer.
This skimmer will react to a lot of things. Water changes, hands in tank, food in tank, chemicals. etc.
Hope this helps. Happy T/g. John