Can't get rid of these bugs

Hey all! I am sort of a newbie at houseplants, have had a few plants for a few months. I've been pretty good at figuring out the different plants' watering schedules, amounts of sunlight, etc. But about two months back, I got a maidenhair fern. It was actually doing pretty ok for a while, but then one day, about three ish weeks ago, I started noticing these tiny bugs that I thought were gnats. No biggie, I sprayed each of my plants with an insecticide and thought the problem was over. But no, it has since gotten worse. These bugs have practically taken over my poor fern, they are all in the soil, and have multiplied. These bugs, as I said, look like tiny gnats, and a quick Google search suggested they were fungus gnats, and to water the plant with a mix of 50/50 water and hydrogen peroxide. I have done that three times since, to no avail. I am not sure what to do at this point, the fern is now living outside due to the amount of bugs now in my small bedroom, from this one plant. I don't want to give up on this fern yet, please, someone with more plant knowledge then me, tell me your secrets!