Also to be noted is that very few mosquitos will lay eggs in moist soil. Of the aprox 3000 species of mosquito, only a few "Floodwater Mosquitoes" will lay eggs in moist soil. And even they need standing water to hatch, as do all mosquitoes.. So if your are noticing them laying eggs and hatching, your soil is likely way to waterlogged.

By any chance are you using the "tilted tank" technique where you put the tank on an angle and let the water create muddy soil on one side and dry soil on the other? Cause I tried that about 10 years ago and my Pac died mysteriously within a week. I never owned a Pac again til about a month ago because of it.