How do I sanitize substrate????

[Draco1264]

I bought from a local garden shop organic worm castings and organic topsoil. I was wondering if I can put them through the microwave to destroy harmful organisms or if I should freeze large bags of the substrate I bought from the flower shop. This is for a giant African bull frog but I treat him with sensitivity like a newt or salamander due to him being so exotic and big don't want to mix the the bad stuff in

 

[Niels D]

Both have worked well for me. Freezing takes some time of course. When using the microwave, choose the highest Wt and keep it in there for 10 minutes just to be sure.