I haven't adjusted mine in two years. Only reason it will fluctuate is if your tank level fluctuates. Or if adding things like chemiclean or anti-planaria potions etc.
My guess is you have a sophisticated auto topoff on that large a system.
That said, spend $100 on a large waste collector with auto shutoff. You must have that just to be sure you avoid disaster.
As for level, every tank is different. You may well be fine there. Depends on bioload how much you fed and what, etc etc. But after a few days you will be fine. MICRO ADJUSTMENTS to the gate valve!!! Tiny adjustments make a huge difference in these skimmers. But once dialed in you are done except when adding as per above (at which time I close the valve in the waste collector all the way. NEVER the gate valve on the skimmer).
What pump did you get????