yeah that DE stuff is a nightmare to clean up, dust everywhere. I won't be using it again. Replaced yellow sticky cards and no adults caught on them after 8 hours so that's gotta be a good sign. I used mosquito dunks, nematodes and neem oil over the past few weeks and it seems to have finally curbed their population. I tried using gognats today but it seems much more suited for aerial spray or hydro rather than a soil add-in, it plummets the water's ph and by the time I get it back to where it needs to be the ppm is too high.
game plan is to start using perlite like someone suggested on the top and bottom of the potted soil and use a mosquito dunk once a month for added measure. I don't recommend using DE to anyone looking to get rid of fungus gnats since there are other more effective ways of dealing with thrips that are less messy and comparable cost.