if he insists cover and seal it with something impermeable a tarp or something. Seriously though thats crazy tell him to try the traps they really so work and will be enormously less expensive (which will propbably be the selling point with a land lord)
If you seal it, then no air gets in, and if no air gets in no gas exchange takes place. Not sure how close your tank is to a window, but if its close you can seal the tank up air tight. Seal a PVC pipe just above the waterline in the tank, and run it out the window and then seal the window. You have to seal the window or the fogger will go out the window and in the PVC. This way you can have gas exchange, same thing like when your pond freezes over in th winter
