Frenchy, I like the 3/16 pumice for smaller pots (like 4 inch and smaller) and 3/8 for larger. I tried the 1/8 previously and had a lot of problems with the pumice compacting into big chunks in the pot. It was like cement. Not sure why that happened. Maybe it was a bad batch or wasn't rinsed well enough?
I've also moved toward using pure pumice for succulents (or pumice and Reptibark for tropicals) rather than mixing it with soil since the soil always ends up collecting at the bottom of the pot.
