hey Starphish, for fingus gnats, i'm like Larimar i use nemadoes, it works and it's bio specifically I'm using Beauveria Bassiana and Metarrhizium against white fly (and not BT which is for other stuff not gnats) . What i dont like about hydrogen peroxyde is that you've ust effectively killed everything alive in the soil which is why we use that stuff as a flushing agent usually. Nonetheless : what you want to do now is revive your soil any way you can maybe by adding beneficials for example Trichoderma Harianum and Bacillus Subtilis, maybe add a bit of a molasses booster to attract... bacteria and flies lol, or some other method to get that soil health you need to grow that high grade. Hope this help ! 🚀