Blood sucking; challenges of controlling populations; disease carrying viruses, protozoa and filarial worms; and inflamed and itchy bites and welts are concerns with 'No-see-ums'. The seemingly invisible, biting insects also are called biting midges and sand flies. They're in the Ceratopogonidae family.
So no-see-ums are related to black flies, of the Simuliidae family. Both like moist environments. Specifically, black flies may be found in natural water bodies such as streams. Their presence actually is an indicator of water pollution. No-see-ums may be found around swimming pools. Such locations may it particularly challenging to control their numbers. But insecticidal soap will do the job if only you can figure out where the invisible biters are coming from and going to!