Mosquito control products kills mosquitoes while they are in a larva state. Mosquito larva are found in standing water where there is no water circulation. If your water garden is circulating its water volume at least once every two hours then mosquito should not attempt to lay eggs in it. Mosquitoes require non-circulating water to grow in.
Places you may have a need for mosquito control is anywhere standing water is present. Places such as bird bathes, livestock water troughs, small farm ponds, etc.