You're going to have to stay on top of this, because there should be eggs hatching in the next couple of weeks which are entirely unaffected by soaking. The easiest thing to do is to get one of the professional remedies (I won't debate the relative merits of each), but you can eventually kill them off the way you're doing it if they don't make it to other hosts (like your beardies or any wild critters that may sneak under your house, etc.).