>>658747Yeah on that pic it looks like dry sand, but is actually a screened garden soil + sand mixture
Made a crappy drawing to explain it better.
Advantages here over using the wet and/or clumpy soil of the pot is that a) because of the powdery structure, any holes fill up more easily b) you're not as likely to damage the roots as if you dropped heavy clumps on them directly and c) the roots are spread out a bit more already from the beginning and not squished together as when you press from the side to refill up the hole
Also rinse the infested roots as good as you can to get rid of as much contaminated soil still sticking there as possible, but of course not too high water pressure
If you're going to use the same pot, clean it with some bleach beforehand, then wash it away well and let it completely dry, as for the soil consider sterilising it in an oven (the inside should reach 80°C for at least half an hour)
