Howdy,
I think several guys/gals are right : You should cover your tank. I suggest a tarp and duct tape. Or a tarp large enough to reach the floor. How tight you need to seal it also depends on if you have a covered tank or if your tank is open.
I also think several guys/gals here are paranoid . Turning off the filters is unnecessary and only puts your fish at risk. Regardless of the filter type, it just circulates your water. That has nothing to do with ambient air. Bubblers are a different story: Turn them off. Since you will cover your tank with a tarp, the movement of the water surface does not have any effect on insectizide deposit.
I have tried glue traps successfully. Especially Brown Recluse will pile up on them, since they prey on their own kind. There are also special insecticides on the market for scorpions and spiders. Use those if spiders are your only problem.
Happy fishkeeping,
HarleyK