m0useanswered grow question 8 months ago These type of products should not cost that much, your doing something very wrong if they do.
BTi or Nematoads for infoor gnat controal.
and if you have access to them try a carnivorous plant, the best ones are Butterworts for trapping and eating gnats, Venusflytraps are not great nor are pitcher plants. Sundews are hit n miss, I got a butterwort in my tent now for my honey mints grow. It caught a lot of them.