Tony,
Cover your tanks and you won't have a problem. If you DO get mosquito larvae growing in the tank a couple of drops of pyrethrin or a mosquito dunk from a garden center will do the trick and will not harm your plants or humans.

Thanks AdrianaG,

That should be easy enough to do in my few systems.

I wasnt sure if they really are aggressive to get in the tanks or not.

Tony

Different mosquitoes have different behaviors. Some mosquitoes lay their eggs on water & some lay their eggs on soil, which in hydroponics would probably be the media. If you have a significant mosquito problem you might want to change nutrient & clean out your system. Take care of any breeding sources that might be contributing to the problem. An air pump in your nutrient may prevent stagnation which promotes breeding. Since mosquitoes rest on vegetation, fine mesh screens (16-18 mesh) to keep them out of your growing area may help. A fan, sticky tapes or mosquito fish may also help.
http://www.mosquito.org/info.php
in the FAQ link says the following of mosquito dunks:
"The only downside is that it must be ingested by mosquito larvae, so it's best used where there are little competing food sources - relatively clean water."

get into aquaponics. Those larve make good food...

A fine mesh sould do the trick even with agressive mosquitos. I would try this method before going to others that may contaminate the nutrients.

Thanks Screener/every one else,

Between the return water and air bubbles, the water is a lil rough maybe for mosquito breeding. SO far, no problems yet.

Tony