Venus flytraps are great plants to keep, but they’re not effective for pest control, especially against tiny gnats. The gnats you have are probably fungus gnats and your houseplants’ soil is infested with their larvae. To get them under control you have to innoculate the soil with nematodes that eat the larvae. The particular brand I got on Amazon aren’t available anymore, but the species was s. feltiae and they worked really well. There might be other good or better nematodes, but that’s how you get rid of the gnats.